ENH: add regex functionality to DataFrame.replace

add default of None to to_replace

add ability to pass regex as to_replace regex

Remove cruft

more tests and add ability to pass regex and value

Make exceptions more clear; push examples to missing_data.rst

remove interpolation call

make inplace work across axes in interpolate method

ability to use nested dicts for regexs and others

mostly doc updates

formatting

infer_types correction

rls notes
DOC: minor edits in missing_data.rst and io/stata edits
BUG: (GH3601) Reindex data if reordering time/period index
Merge pull request #3619 from dieterv77/FixGH3601

BUG: (GH3601) Reindex data if reordering time/period index
DOC: correct mpl_style option name in whatsnew.html GH3640
DOC: CONTRIBUTING.md
Merge remote-tracking branch 'pandas_upstream/master'