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: add guidelines for building the docs
DOC: add section contributing to pandas

+ link to README.rst in /docs
DOC: Clarify that DataFrame string formatters must return strings

I am not 100% sure that string formatters must really return *unicode* strings
(non-unicode strings seem to work, too), but I am leaving that because it's
what is already documentated.

Fixes #6052.
CLN: add clarifying comment to ipython_directive.py
DOC: Explain the use of NDFrame.equals
BLD/DOC: add context info on exception during sphinx run
Merge pull request #6075 from y-p/PR_ipython_directive_context

Pr ipython directive context
Merge pull request #6072 from unutbu/doc-equals

DOC: Explain the use of NDFrame.equals
TST: fix test_eval typos
Merge pull request #6074 from dsm054/fix-test_eval

TST: Fix test_eval.py
DOC/BUG: Fix documentation for `infer_datetime_format` #6073

Fix formatting typos and ensure the "foo.csv" ipython processing works.
Merge pull request #6078 from danbirken/infer-dt-doc-fix

DOC/BUG: Fix documentation for `infer_datetime_format` #6073
Merge pull request #5996 from jorisvandenbossche/doc-guide

DOC: add guidelines for building the docs
BLD/DOC: report context on warnings and add :okwarning: to ipython_directive
Merge pull request #6082 from y-p/PR_ipython_directive

BLD/DOC: report context on warnings and add :okwarning: to ipython_directive
DOC/BLD: ipython_directive cleanups
DOC: minor doc changes
Added 'Experimental' to Docstrings
Merge pull request #6084 from jacobschaer/master

Added 'Experimental' to Docstrings For GBQ