ENH: TimedeltaIndex and Timedelta scalar support (GH3009)

BUG: coercion of timedeltas in assignment (GH8209)

COMPAT: provide conversion for passing in non-ns datetime64/timedelta64

BUG: diff on Dataframe with timedelta64 broken (GH4533)

ENH: support for alternate Timedelta format constructors in natural language (GH8190)

BUG: handle empty timedelta64[ns] Series with ops (GH7869)
Merge pull request #8184 from jreback/tdi

ENH: create Timedelta scalar / TimedeltaIndex