Grouping, then resampling empty DataFrame leads to it losing column names and index
#### Code Sample

```python
import pandas as pd

empty_df = pd.DataFrame([], columns=["a", "b"], index=pd.TimedeltaIndex([]))

resampled_df = empty_df.groupby("a").resample(rule=pd.to_timedelta("00:00:01")).mean()

print resampled_df
print resampled_df["b"]
```
#### Problem description

After grouping and subsequently resampling as shown above, the returned data frame seems to lose all its meta information, such as column names and what type of index it uses. This leads to a key error when trying to access columns of the data frame that were existent, but empty, before doing the grouping and resampling.

Perhaps somewhere in the code a "generic" empty data frame is returned without the attached information about column names and indices?

#### Expected Output

```
Empty DataFrame
Columns: [a, b]
Index: []
Series([], Name: b, dtype: object) 
```

or similar, and `empty_df["b"] == resampled_df["b"]` would make sense to me.

#### Actual Output

```
Empty DataFrame
Columns: []
Index: []
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/frame.py", line 2927, in __getitem__
    indexer = self.columns.get_loc(key)
  File "/usr/local/lib/python2.7/dist-packages/pandas/core/indexes/base.py", line 2659, in get_lo
    return self._engine.get_loc(self._maybe_cast_indexer(key))
  File "pandas/_libs/index.pyx", line 108, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/index.pyx", line 132, in pandas._libs.index.IndexEngine.get_loc
  File "pandas/_libs/hashtable_class_helper.pxi", line 1601, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas/_libs/hashtable_class_helper.pxi", line 1608, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 'b'  
```

#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS                                                                                                                                                                                                                             ------------------                                                                                                                                                                                                                             commit: None                                                                                                                                                                                                                                   python: 2.7.12.final.0                                                                                                                                                                                                                         python-bits: 64                                                                                                                                                                                                                                OS: Linux                                                                                                                                                                                                                                      OS-release: 4.9.93-linuxkit-aufs                                                                                                                                                                                                               machine: x86_64                                                                                                                                                                                                                                processor: x86_64                                                                                                                                                                                                                              byteorder: little                                                                                                                                                                                                                              LC_ALL: C.UTF-8                                                                                                                                                                                                                                LANG: C.UTF-8                                                                                                                                                                                                                                  LOCALE: None.None                                                                                                                                                                                                                                                                                                                                                                                                                                                                             pandas: 0.24.2                                                                                                                                                                                                                                 pytest: None                                                                                                                                                                                                                                   pip: 8.1.1                                                                                                                                                                                                                                     setuptools: 20.7.0                                                                                                                                                                                                                             Cython: None                                                                                                                                                                                                                                   numpy: 1.16.2                                                                                                                                                                                                                                  scipy: 0.17.0                                                                                                                                                                                                                                  pyarrow: None                                                                                                                                                                                                                                  xarray: None                                                                                                                                                                                                                                   IPython: None                                                                                                                                                                                                                                  sphinx: 1.3.6                                                                                                                                                                                                                                  patsy: None                                                                                                                                                                                                                                    dateutil: 2.8.0                                                                                                                                                                                                                                pytz: 2018.9                                                                                                                                                                                                                                   blosc: None                                                                                                                                                                                                                                    bottleneck: None                                                                                                                                                                                                                               tables: 3.5.1                                                                                                                                                                                                                                  numexpr: 2.6.9                                                                                                                                                                                                                                 feather: None                                                                                                                                                                                                                                  matplotlib: 1.5.1                                                                                                                                                                                                                              openpyxl: None                                                                                                                                                                                                                                 xlrd: None                                                                                                                                                                                                                                     xlwt: None                                                                                                                                                                                                                                     xlsxwriter: None                                                                                                                                                                                                                               lxml.etree: 3.5.0                                                                                                                                                                                                                              bs4: 4.4.1                                                                                                                                                                                                                                     html5lib: 0.999                                                                                                                                                                                                                                sqlalchemy: 1.3.1                                                                                                                                                                                                                              pymysql: 0.7.2.None                                                                                                                                                                                                                            psycopg2: None                                                                                                                                                                                                                                 jinja2: 2.10                                                                                                                                                                                                                                   s3fs: None                                                                                                                                                                                                                                     fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None
</details>
