BUG: Fix DatetimeIndex.insert() with non-datetimes.

Coerces to object Index instead.
COMPAT: allow string concats to datetimeindex only (int/float are invalid)
BUG: Fix to_datetime to properly deal with tz offsets #3944

Currently for certain formats of datetime strings, the tz offset will
just be ignored.
DOC: moved numpydoc sphinx extension to subdirectory

Clearer distinction from ipython directive files
DOC: update numpydoc to current master (commit 223df02530)
DOC: release.rst mention IPython warnings in qtconsole fix and workaround GH5922
CLN: remove util.counter, duplicates compat
BLD: travis, Install apt-get deps first
BLD: travis, future-proof pip args
Merge pull request #6017 from y-p/PR_cln_counter

Remove duplicated code and fix travis
ENH: improved inference of timedelta64[ns] and datetime64[ns] in the prescence NaT/None/NaN
     from object dtypes (GH5689)
CLN: refactor of timedelta routines to cython for inclusion in maybe_convert_objects
BUG: apply to a Series with a timedelta (GH5458)
ENH: improved timedelta inference for non-ns dtypes
BUG: timedelta64 merge/join issues (GH5695)
DOC: release note for timedelta changes

TST: skip tests on numpy < 1.7 as needed for timedeltas

BUG: fixup .abs for timedeltas
Merge pull request #5995 from jreback/timedelta_fixes

BUG/CLN: clarified timedelta inferences
DOC: make zipped HTML docs available GH1876
Merge pull request #6020 from y-p/PR_GH1876

DOC: make zipped HTML docs available GH1876
DOC: update mailing list
TST: remove test.py (accidently added)
DOC: fix parser docstring for 'quotechar', 'quoting' params; closes #5408