str_extract should work for timeseries, bug 6348
BLD: remove pdb from test_strings.py
BLD: add numpy 1.8.x builds as optional
ENH: Preserve .names in df.set_index(df.index)

Preserve .names in df.set_index(df.index)

Check that df.set_index(df.index) doesn't convert a MultiIndex to an Index