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

Coerces to object Index instead.
COMPAT: allow string concats to datetimeindex only (int/float are invalid)
DOC: moved numpydoc sphinx extension to subdirectory

Clearer distinction from ipython directive files
DOC: update numpydoc to current master (commit 223df02530)
DOC: add guidelines for building the docs
DOC: add section contributing to pandas

+ link to README.rst in /docs
PERF: Speed up pd.to_datetime() by optionally inferring dt format #5490

Given an array of strings that represent datetimes, infer_format=True
will attempt to guess the format of the datetimes, and if it can infer
the format, it will use a faster function to convert/import the
datetimes.  In cases where this speed-up can be used, the function
should be about 10x faster.
PERF: Add infer_datetime_format to read_csv() #5490

This allows read_csv() to attempt to infer the datetime format for any
columns where parse_dates is enabled.  In cases where the datetime
format can be inferred, this should speed up processing datetimes
by ~10x.

Additionally add documentation and benchmarks for read_csv().
TST/DOC: addtl tests and docs for (GH6056)
Merge pull request #6058 from jreback/iloc_segfault

TST/DOC: addtl tests and docs for (GH6056)
BLD: add IPython and sphinx to show_versions #6059
Merge pull request #6064 from y-p/PR_add_deps_show_versions

BLD: add IPython and sphinx to show_versions #6059
Merge pull request #6003 from jorisvandenbossche/numpydoc

DOC: update numpydoc to current master (commit 223df02530)
API: Add equals method to NDFrames. (Implemented with `array_equivalent`, which is similar to `np.array_equal` except that it handles object arrays and treats NaNs in corresponding locations as equal.

TST: Add tests for NDFrame.equals and BlockManager.equals

DOC: Mention the equals method in basics, release and v.0.13.1
BUG: suble iloc indexing bug with single block and multi-axis indexing
DOC: pytables iterator update
Merge pull request #5283 from unutbu/array-equivalent

API: Add equals method to NDFrames.
Merge pull request #6065 from jreback/iloc_bug

BUG: suble iloc indexing bug with single block and multi-axis indexing (surfaced in GH6059)
Merge pull request #6021 from danbirken/infer-datetime-format

Infer datetime format
DOC: update release notes