DOC/BLD: Update version support in docs and setup.py.
Merge pull request #4530 from jtratner/update-version-support-in-docs

DOC/BLD: Update version support in docs and setup.py.
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