0.13rc1+ vs. 0.12 vbench, perf regressions.
30% slowdown and up.

```
melt_dataframe                               |   2.7920 |   2.1487 |   1.2994 |
concat_small_frames                          |  22.1807 |  17.0054 |   1.3043 |
dti_reset_index                              |   0.2950 |   0.2257 |   1.3070 |
frame_reindex_upcast                         |  28.8033 |  21.2270 |   1.3569 |
frame_fancy_lookup_all                       |  30.4507 |  22.1930 |   1.3721 |
timeseries_large_lookup_value                |   0.0383 |   0.0277 |   1.3811 |
frame_boolean_row_select                     |   0.4419 |   0.3170 |   1.3941 |
panel_from_dict_equiv_indexes                |  58.9810 |  41.6213 |   1.4171 |
panel_from_dict_same_index                   |  58.9364 |  41.5120 |   1.4197 |
frame_xs_row                                 |   0.0637 |   0.0443 |   1.4355 |
groupby_frame_singlekey_integer              |   4.3193 |   2.9940 |   1.4427 |
frame_ctor_nested_dict                       | 142.8297 |  98.7384 |   1.4465 |
frame_to_csv2                                | 191.4937 | 130.7974 |   1.4640 |
series_ctor_from_dict                        |   5.1107 |   3.4617 |   1.4764 |
groupby_multi_python                         | 175.8397 | 117.9717 |   1.4905 |
frame_to_csv                                 | 237.1720 | 154.0547 |   1.5395 |
series_string_vector_slice                   | 325.1186 | 208.9640 |   1.5559 |
indexing_panel_subset                        |   0.9351 |   0.5874 |   1.5919 |
frame_insert_500_columns_end                 | 198.1669 | 124.3424 |   1.5937 |
frame_ctor_nested_dict_int64                 | 173.6054 | 106.8807 |   1.6243 |
frame_loc_dups                               |   1.2674 |   0.7770 |   1.6311 |
frame_get_dtype_counts                       |   0.1843 |   0.1113 |   1.6552 |
ctor_index_array_string                      |   0.0393 |   0.0236 |   1.6667 |
frame_get_numeric_data                       |   0.1736 |   0.0997 |   1.7424 |
frame_constructor_ndarray                    |   0.1047 |   0.0587 |   1.7846 |
frame_iteritems_cached                       |   1.1443 |   0.6117 |   1.8707 |
indexing_dataframe_boolean_rows_object       |   0.9307 |   0.4853 |   1.9176 |
reshape_stack_simple                         |   2.6710 |   1.3684 |   1.9520 |
frame_iloc_dups                              |   0.5160 |   0.2420 |   2.1323 |
frame_xs_col                                 |   0.0720 |   0.0323 |   2.2260 |
dataframe_getitem_scalar                     |   0.0199 |   0.0087 |   2.3028 |
datamatrix_getitem_scalar                    |   0.0193 |   0.0083 |   2.3143 |
indexing_dataframe_boolean_rows              |   0.5593 |   0.2393 |   2.3374 |
series_constructor_ndarray                   |   0.0397 |   0.0167 |   2.3762 |
sparse_frame_constructor                     |  13.0450 |   4.7807 |   2.7287 |
frame_iteritems                              |  76.1917 |  27.6610 |   2.7545 |
indexing_frame_get_value_ix                  |   0.0123 |   0.0044 |   2.8182 |
series_getitem_scalar                        |   0.0199 |   0.0070 |   2.8523 |
frame_from_series                            |   0.1774 |   0.0534 |   3.3214 |
frame_fancy_lookup                           |   7.8727 |   1.7236 |   4.5675 |
series_get_value                             |   0.0123 |   0.0017 |   7.3810 |
```

**Ruled out**

```
frame_repr_tall                              |  49.2450 |   2.3817 |  20.6762 |
frame_repr_wide                              | 977.6090 |   1.1230 | 870.5710 |
```
#5550: truncated repr for large frames. legitimate change.
