CLN: ASV io benchmarks
[xref](https://github.com/pandas-dev/pandas/pull/18815#issuecomment-352723075)

Consolidated the benchmarks from `io_sql.py`, `hdfstore_bench.py`, and `packers.py` into their own files in the `io` folder. Benchmarks are largely the same as they were, just cleaned and simplified where able.

```
asv dev -b ^io
· Discovering benchmarks
· Running 67 total benchmarks (1 commits * 1 environments * 67 benchmarks)
[  0.00%] ·· Building for existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  0.00%] ·· Benchmarking existing-py_home_matt_anaconda_envs_pandas_dev_bin_python
[  1.49%] ··· Running io.csv.ReadCSVCategorical.time_convert_direct                                                                   98.5ms
[  2.99%] ··· Running io.csv.ReadCSVCategorical.time_convert_post                                                                      142ms
[  4.48%] ··· Running io.csv.ReadCSVComment.time_comment                                                                              53.6ms
[  5.97%] ··· Running io.csv.ReadCSVDInferDatetimeFormat.time_read_csv                                                                    ok
[  5.97%] ···· 
               ======================= ======== ========= ========
               --                                 format          
               ----------------------- ---------------------------
                infer_datetime_format   custom   iso8601    ymd   
               ======================= ======== ========= ========
                         True           24.4ms    4.73ms   4.99ms 
                        False           662ms     3.50ms   3.23ms 
               ======================= ======== ========= ========

[  7.46%] ··· Running io.csv.ReadCSVFloatPrecision.time_read_csv                                                                          ok
[  7.46%] ···· 
               ===== ========== ========== ================ ========== ========== ================
               --                              decimal / float_precision                          
               ----- -----------------------------------------------------------------------------
                sep   . / None   . / high   . / round_trip   _ / None   _ / high   _ / round_trip 
               ===== ========== ========== ================ ========== ========== ================
                 ,     3.91ms     3.77ms        5.52ms        4.25ms     4.19ms        4.20ms     
                 ;     3.86ms     3.73ms        5.56ms        4.16ms     4.23ms        4.13ms     
               ===== ========== ========== ================ ========== ========== ================

[  8.96%] ··· Running io.csv.ReadCSVFloatPrecision.time_read_csv_python_engine                                                            ok
[  8.96%] ···· 
               ===== ========== ========== ================ ========== ========== ================
               --                              decimal / float_precision                          
               ----- -----------------------------------------------------------------------------
                sep   . / None   . / high   . / round_trip   _ / None   _ / high   _ / round_trip 
               ===== ========== ========== ================ ========== ========== ================
                 ,     8.54ms     8.44ms        8.50ms        7.03ms     6.99ms        6.99ms     
                 ;     8.46ms     8.53ms        8.42ms        7.00ms     7.09ms        7.00ms     
               ===== ========== ========== ================ ========== ========== ================

[ 10.45%] ··· Running io.csv.ReadCSVParseDates.time_baseline                                                                          2.86ms
[ 11.94%] ··· Running io.csv.ReadCSVParseDates.time_multiple_date                                                                     2.85ms
[ 13.43%] ··· Running io.csv.ReadCSVSkipRows.time_skipprows                                                                               ok
[ 13.43%] ···· 
               ========== ========
                skiprows          
               ---------- --------
                  None     46.1ms 
                 10000     31.4ms 
               ========== ========

[ 14.93%] ··· Running io.csv.ReadCSVThousands.time_thousands                                                                              ok
[ 14.93%] ···· 
               ===== ======== ========
               --        thousands    
               ----- -----------------
                sep    None      ,    
               ===== ======== ========
                 ,    38.6ms   35.6ms 
                 |    38.9ms   38.6ms 
               ===== ======== ========

[ 16.42%] ··· Running io.csv.ReadUint64Integers.time_read_uint64                                                                      8.95ms
[ 17.91%] ··· Running io.csv.ReadUint64Integers.time_read_uint64_na_values                                                            13.0ms
[ 19.40%] ··· Running io.csv.ReadUint64Integers.time_read_uint64_neg_values                                                           13.0ms
[ 20.90%] ··· Running io.csv.S3.time_read_csv_10_rows                                                                                     ok
[ 20.90%] ···· 
               ============= ======== =======
               --                 engine     
               ------------- ----------------
                compression   python     c   
               ============= ======== =======
                    None      8.43s    6.27s 
                    gzip      6.80s    7.74s 
                    bz2       36.6s     n/a  
               ============= ======== =======

[ 22.39%] ··· Running io.csv.ToCSV.time_frame                                                                                             ok
[ 22.39%] ···· 
               ======= ========
                 kind          
               ------- --------
                 wide   89.1ms 
                 long   172ms  
                mixed   38.6ms 
               ======= ========

[ 23.88%] ··· Running io.csv.ToCSVDatetime.time_frame_date_formatting                                                                 23.1ms
[ 25.37%] ··· Running io.excel.Excel.time_read_excel                                                                                      ok
[ 25.37%] ···· 
               ============ =======
                  engine           
               ------------ -------
                 openpyxl    565ms 
                xlsxwriter   569ms 
                   xlwt      158ms 
               ============ =======

[ 26.87%] ··· Running io.excel.Excel.time_write_excel                                                                                     ok
[ 26.87%] ···· 
               ============ =======
                  engine           
               ------------ -------
                 openpyxl    1.24s 
                xlsxwriter   970ms 
                   xlwt      704ms 
               ============ =======

[ 28.36%] ··· Running io.hdf.HDF.time_read_hdf                                                                                            ok
[ 28.36%] ···· 
               ======== ========
                format          
               -------- --------
                table    63.0ms 
                fixed    79.8ms 
               ======== ========

[ 29.85%] ··· Running io.hdf.HDF.time_write_hdf                                                                                           ok
[ 29.85%] ···· 
               ======== =======
                format         
               -------- -------
                table    121ms 
                fixed    149ms 
               ======== =======

[ 31.34%] ··· Running io.hdf.HDFStoreDataFrame.time_query_store_table                                                                 26.4ms
[ 32.84%] ··· Running io.hdf.HDFStoreDataFrame.time_query_store_table_wide                                                            33.2ms
[ 34.33%] ··· Running io.hdf.HDFStoreDataFrame.time_read_store                                                                        12.1ms
[ 35.82%] ··· Running io.hdf.HDFStoreDataFrame.time_read_store_mixed                                                                  25.4ms
[ 37.31%] ··· Running io.hdf.HDFStoreDataFrame.time_read_store_table                                                                  18.0ms
[ 38.81%] ··· Running io.hdf.HDFStoreDataFrame.time_read_store_table_mixed                                                            36.6ms
[ 40.30%] ··· Running io.hdf.HDFStoreDataFrame.time_read_store_table_wide                                                             30.1ms
[ 41.79%] ··· Running io.hdf.HDFStoreDataFrame.time_store_info                                                                        53.2ms
[ 43.28%] ··· Running io.hdf.HDFStoreDataFrame.time_store_repr                                                                         112μs
[ 44.78%] ··· Running io.hdf.HDFStoreDataFrame.time_store_str                                                                          109μs
[ 46.27%] ··· Running io.hdf.HDFStoreDataFrame.time_write_store                                                                       13.6ms
[ 47.76%] ··· Running io.hdf.HDFStoreDataFrame.time_write_store_mixed                                                                 31.6ms
[ 49.25%] ··· Running io.hdf.HDFStoreDataFrame.time_write_store_table                                                                 45.1ms
[ 50.75%] ··· Running io.hdf.HDFStoreDataFrame.time_write_store_table_dc                                                               357ms
[ 52.24%] ··· Running io.hdf.HDFStoreDataFrame.time_write_store_table_mixed                                                           56.7ms
[ 53.73%] ··· Running io.hdf.HDFStoreDataFrame.time_write_store_table_wide                                                             160ms
[ 55.22%] ··· Running io.hdf.HDFStorePanel.time_read_store_table_panel                                                                55.2ms
[ 56.72%] ··· Running io.hdf.HDFStorePanel.time_write_store_table_panel                                                               90.3ms
[ 58.21%] ··· Running io.json.ReadJSON.time_read_json                                                                                     ok
[ 58.21%] ···· 
               ========= ======= ==========
               --              index       
               --------- ------------------
                 orient    int    datetime 
               ========= ======= ==========
                 split    253ms    270ms   
                 index    7.80s    7.97s   
                records   619ms    627ms   
               ========= ======= ==========

[ 59.70%] ··· Running io.json.ReadJSONLines.peakmem_read_json_lines                                                                       ok
[ 59.70%] ···· 
               ========== ======
                 index          
               ---------- ------
                  int      192M 
                datetime   192M 
               ========== ======

[ 61.19%] ··· Running io.json.ReadJSONLines.peakmem_read_json_lines_concat                                                                ok
[ 61.19%] ···· 
               ========== ======
                 index          
               ---------- ------
                  int      164M 
                datetime   164M 
               ========== ======

[ 62.69%] ··· Running io.json.ReadJSONLines.time_read_json_lines                                                                          ok
[ 62.69%] ···· 
               ========== =======
                 index           
               ---------- -------
                  int      734ms 
                datetime   740ms 
               ========== =======

[ 64.18%] ··· Running io.json.ReadJSONLines.time_read_json_lines_concat                                                                   ok
[ 64.18%] ···· 
               ========== =======
                 index           
               ---------- -------
                  int      767ms 
                datetime   763ms 
               ========== =======

[ 65.67%] ··· Running io.json.ToJSON.time_delta_int_tstamp                                                                                ok
[ 65.67%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    347ms 
                columns   353ms 
                 index    400ms 
               ========= =======

[ 67.16%] ··· Running io.json.ToJSON.time_delta_int_tstamp_lines                                                                          ok
[ 67.16%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    634ms 
                columns   643ms 
                 index    632ms 
               ========= =======

[ 68.66%] ··· Running io.json.ToJSON.time_float_int                                                                                       ok
[ 68.66%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    232ms 
                columns   233ms 
                 index    389ms 
               ========= =======

[ 70.15%] ··· Running io.json.ToJSON.time_float_int_lines                                                                                 ok
[ 70.15%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    684ms 
                columns   686ms 
                 index    685ms 
               ========= =======

[ 71.64%] ··· Running io.json.ToJSON.time_float_int_str                                                                                   ok
[ 71.64%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    354ms 
                columns   231ms 
                 index    411ms 
               ========= =======

[ 73.13%] ··· Running io.json.ToJSON.time_float_int_str_lines                                                                             ok
[ 73.13%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    713ms 
                columns   713ms 
                 index    714ms 
               ========= =======

[ 74.63%] ··· Running io.json.ToJSON.time_floats_with_dt_index                                                                            ok
[ 74.63%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    191ms 
                columns   222ms 
                 index    220ms 
               ========= =======

[ 76.12%] ··· Running io.json.ToJSON.time_floats_with_dt_index_lines                                                                      ok
[ 76.12%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    531ms 
                columns   527ms 
                 index    533ms 
               ========= =======

[ 77.61%] ··· Running io.json.ToJSON.time_floats_with_int_idex_lines                                                                      ok
[ 77.61%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    525ms 
                columns   525ms 
                 index    524ms 
               ========= =======

[ 79.10%] ··· Running io.json.ToJSON.time_floats_with_int_index                                                                           ok
[ 79.10%] ···· 
               ========= =======
                 orient         
               --------- -------
                 split    167ms 
                columns   183ms 
                 index    194ms 
               ========= =======

[ 80.60%] ··· Running io.msgpack.MSGPack.time_read_msgpack                                                                            48.2ms
[ 82.09%] ··· Running io.msgpack.MSGPack.time_write_msgpack                                                                           73.5ms
[ 83.58%] ··· Running io.pickle.Pickle.time_read_pickle                                                                                110ms
[ 85.07%] ··· Running io.pickle.Pickle.time_write_pickle                                                                               157ms
[ 86.57%] ··· Running io.sas.SAS.time_read_msgpack                                                                                        ok
[ 86.57%] ···· 
               ========== ========
                 format           
               ---------- --------
                sas7bdat   608ms  
                 xport     9.92ms 
               ========== ========

[ 88.06%] ··· Running io.sql.ReadSQLTable.time_read_sql_table_all                                                                         ok
[ 88.06%] ···· 
               ================ =======
                    dtype              
               ---------------- -------
                    float        101ms 
                float_with_nan   101ms 
                    string       101ms 
                     bool        102ms 
                     int         101ms 
                   datetime      101ms 
               ================ =======

[ 89.55%] ··· Running io.sql.ReadSQLTable.time_read_sql_table_column                                                                      ok
[ 89.55%] ···· 
               ================ ========
                    dtype               
               ---------------- --------
                    float        24.1ms 
                float_with_nan   23.0ms 
                    string       25.1ms 
                     bool        23.8ms 
                     int         25.6ms 
                   datetime      46.6ms 
               ================ ========

[ 91.04%] ··· Running io.sql.ReadSQLTable.time_read_sql_table_parse_dates                                                                 ok
[ 91.04%] ···· 
               ================ ========
                    dtype               
               ---------------- --------
                    float        31.5ms 
                float_with_nan   31.9ms 
                    string       31.0ms 
                     bool        30.9ms 
                     int         31.2ms 
                   datetime      31.5ms 
               ================ ========

[ 92.54%] ··· Running io.sql.SQL.time_read_sql_query_select_all                                                                           ok
[ 92.54%] ···· 
               ============ ======== ================ ======== ======== ======== ==========
               --                                        dtype                             
               ------------ ---------------------------------------------------------------
                connection   float    float_with_nan   string    bool     int     datetime 
               ============ ======== ================ ======== ======== ======== ==========
                sqlalchemy   70.6ms       71.0ms       70.8ms   70.4ms   70.6ms    71.5ms  
                  sqlite     58.7ms       58.1ms       58.0ms   57.7ms   58.5ms    58.2ms  
               ============ ======== ================ ======== ======== ======== ==========

[ 94.03%] ··· Running io.sql.SQL.time_read_sql_query_select_column                                                                        ok
[ 94.03%] ···· 
               ============ ======== ================ ======== ======== ======== ==========
               --                                        dtype                             
               ------------ ---------------------------------------------------------------
                connection   float    float_with_nan   string    bool     int     datetime 
               ============ ======== ================ ======== ======== ======== ==========
                sqlalchemy   71.6ms       70.6ms       71.5ms   70.8ms   70.8ms    70.4ms  
                  sqlite     58.4ms       58.8ms       58.4ms   57.8ms   57.7ms    58.1ms  
               ============ ======== ================ ======== ======== ======== ==========

[ 95.52%] ··· Running io.sql.SQL.time_to_sql_dataframe_colums                                                                             ok
[ 95.52%] ···· 
               ============ ======== ================ ======== ======== ======== ==========
               --                                        dtype                             
               ------------ ---------------------------------------------------------------
                connection   float    float_with_nan   string    bool     int     datetime 
               ============ ======== ================ ======== ======== ======== ==========
                sqlalchemy   140ms        149ms        136ms    148ms    135ms     257ms   
                  sqlite     54.4ms       63.2ms       55.5ms   92.4ms   52.7ms    118ms   
               ============ ======== ================ ======== ======== ======== ==========

[ 97.01%] ··· Running io.sql.SQL.time_to_sql_dataframe_full                                                                               ok
[ 97.01%] ···· 
               ============ ======= ================ ======== ======= ======= ==========
               --                                      dtype                            
               ------------ ------------------------------------------------------------
                connection   float   float_with_nan   string    bool    int    datetime 
               ============ ======= ================ ======== ======= ======= ==========
                sqlalchemy   435ms       440ms        433ms    436ms   436ms    435ms   
                  sqlite     185ms       186ms        185ms    186ms   185ms    186ms   
               ============ ======= ================ ======== ======= ======= ==========

[ 98.51%] ··· Running io.stata.Stata.time_read_stata                                                                                      ok
[ 98.51%] ···· 
               =============== =======
                convert_dates         
               --------------- -------
                      tc        514ms 
                      td        510ms 
                      tm        1.35s 
                      tw        1.27s 
                      th        1.36s 
                      tq        1.35s 
                      ty        1.76s 
               =============== =======

[100.00%] ··· Running io.stata.Stata.time_write_stata                                                                                     ok
[100.00%] ···· 
               =============== =======
                convert_dates         
               --------------- -------
                      tc        593ms 
                      td        592ms 
                      tm        603ms 
                      tw        1.34s 
                      th        624ms 
                      tq        616ms 
                      ty        592ms 
               =============== =======
```