BUG: (GH4532) Fix bug in having a rhs of np.timedelta64 or np.offsets.DateOffset when operating
     with datetimes
BUG: (GH4134) Fix arithmetic with series/datetimeindex and np.timedelta64 not working the same

TST: add in @cpcloud tests related to GH4135
ENH: GH4521 A Series of dtype timedelta64[ns] can now be divided/multipled by an integer series
DOC/ENH: timedelta conversions & docs

TST: add tests/catch for non-absolute DateOffsets in timedelta operations
Merge pull request #4534 from jreback/td

BUG/API: Fix operating with timedelta64/pd.offsets on rhs of a datelike series/index