FIX: change initObjToJSON return type

This is necessary because clang complains about the return type. There's a call
to the macro import_array() which injects a return statement into wherever it's
used.
BUG/CLN: remove infer_types
BUG: fix bug with replace when a compiled regex was passed but regex=False
TST: add tests for new com functions
DOC: add release notes, whatsnew and consolidate replace API changes
BUG: (GH3911) groupby appying with custom function resulting in frame did not convert dtypes

     on the result object
Merge pull request #3913 from jreback/groupby_apply

BUG: (GH3911) groupby appying with custom function not converting dtypes of result
Merge pull request #3874 from cpcloud/c-ujson-fix

FIX: change initObjToJSON return type
Merge branch 'replace-convert-dtypes-3907' of https://github.com/cpcloud/pandas into cpcloud-replace-convert-dtypes-3907

Conflicts:
	RELEASE.rst