DOC: timedelta return type
#### Location of the documentation

https://github.com/pandas-dev/pandas/blob/master/pandas/core/tools/timedeltas.py#L70

#### Documentation problem

Is `numpy.array of timedelta64` the correct return time for to_timedelta? I see it here as `TimedeltaIndex`: https://github.com/pandas-dev/pandas/blob/master/pandas/tests/indexes/timedeltas/test_timedelta.py#L27

