Holiday.dates always fails with tz-aware input
The conversion from `start_date` to `base_date` on https://github.com/pydata/pandas/blob/master/pandas/tseries/holiday.py#L206 drops tz information, which causes the `DatetimeIndex` constructor to barf if end_date is tz-aware.  Fixed by https://github.com/pydata/pandas/pull/9824.
