ENH: Allow abs to work with PandasObjects
Merge pull request #4821 from jtratner/add-__abs__-method

ENH: Allow abs to work with PandasObjects
DOC: doc build fixes
DOC: expand gotchas/basics on boolean reductions
ENH: support timedelta64[ns] as a serialization type in HDFStore for query and append (GH3577)
CLN: refactored locations of timedeltas to core/tseries/timedeltas (from a series of functions in core/common)
TST: add pandas/tseries/tests/test_timedeltas.py
API: add full timedelta parsing and conversion to np.timedelta64[ns]
ENH: add top-level to_timedelta to convert string/integer based to timedeltas