BUG: TimedeltaIndex slicing may reset freq

[sinhrks]

DatetimeIndex preserve freq after slicing.

di = pd.date_range('2001', '2005', freq='D')
di[1:5:2]
# DatetimeIndex(['2001-01-02', '2001-01-04'], dtype='datetime64[ns]', freq='2D', tz=None)

But TimedeltaIndex doesn't.

tdi = pd.timedelta_range('1day', '5day', freq='D')
tdi[1:5:2]
# TimedeltaIndex(['2 days', '4 days'], dtype='timedelta64[ns]', freq=None)

[jreback]

thanks you sir!