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

Coerces to object Index instead.
COMPAT: allow string concats to datetimeindex only (int/float are invalid)
DOC: r match function
Update comparison_with_r.rst

rm index
Update comparison_with_r.rst
BLD: Explicitly request utf-8 encoding in docs conf.py (is default)
DOC: suppress warning during doc building
BUG: pd.match not returning passed sentinel
Merge pull request #5943 from jreback/match

BUG: pd.match not returning passed sentinel
Update comparison_with_r.rst
BUG/API: autocorrelation_plot should accept kwargs
BUG: Panel.to_frame() with MultiIndex major axis

Fixes bug that caused failure on Panel.to_frame()
if major_axis was a MultiIndex (#5402)

refactor reindexing to index.py

API/REF: refactor bits to index. rename
Merge pull request #5623 from TomAugspurger/autocorr_kwds

BUG/API: autocorrelation_plot should accept kwargs
Merge pull request #5417 from TomAugspurger/to-frame-multi

BUG: Panel.to_frame() with MultiIndex major axis
Merge pull request #5875 from chappers/r-isin

DOC: Add %in% operator into compare w r (GH3850)
BUG: Bug in pd.read_msgpack with inferring a DateTimeIndex frequencey
     incorrectly (GH5947)
CLN: repr_html raises NotImplementedError rather then ValueError in qtconsole GH5922
ENH: Improve perf of str_extract
Merge pull request #5948 from jreback/msgpack_bug

BUG: Bug in pd.read_msgpack with inferring a DateTimeIndex frequency incorrectly (GH5947)
DOC: move _templates out of source/ files to avoid warning