BUG: Add reduce_if_possible keyword to ``groupby`` to allow reduction from

    DataFrame -> Series if groups are unique. Regression from 0.10.1,
    partial revert on (GH2893_) with (GH3596_)

CLN: renamed reduce_if_possible -> squeeze

DOC: added v0.11.1 example
Merge pull request #3599 from jreback/groupby_output

BUG: Add squeeze keyword to groupby to allow reduction in returned type
document read_csv's usecols argument.
Merge pull request #3544 from lexual/read_csv_doc_usecols

document read_csv's usecols argument.
BUG: (GH3611) Fix read_csv to correctly encode identical na_values, e.g. na_values=[-999.0,-999] was failing
Merge pull request #3615 from jreback/read_csv_na_values

BUG: (GH3611) Fix read_csv to correctly encode identical na_values
BUG: (GH3617) Fix indexing issue with ndim >= 3 with iloc
ENH: Added StataReader and StataWriter (#1512)
[ENH] Added support for reading Stata formats 104, 105 and 108
Improvements to StataParser:
- Moved unit test data to tests/data
- Added unit testing for old Stata formats (SKIP per default)
- Use py3compat.PY3 instead of own implementation
Moved StataParser into new module pandas.io.stata
Fixed several problems in StataParser with Travis and Python2.
- Don't call encode/decode on python2
- Added .dta type to setup.py
- Fixed null byte
Added StataParser to release notes and updated io.rst
Merge branch 'master' of https://github.com/PKEuS/pandas into PKEuS-master

Conflicts:
	RELEASE.rst
Merge pull request #3618 from jreback/iloc_broken

BUG: (GH3617) Fix indexing issue with ndim >= 3 with iloc
BUG: fixed platform int issues on 32-bit
Merge pull request #3620 from jreback/tests_fail_fix

BUG: fixed platform int issues on 32-bit
BUG: (GH3062) Correctly parse date columns with embedded (nan/NaT) into datetime64[ns] dtype in ``read_csv``

    when ``parse_dates`` is specified
Merge pull request #3621 from jreback/nat

BUG: (GH3062) Correctly parse date columns with embedded (nan/NaT) into datetime64[ns] in read_csv
DOC: more informative PerformanceWarning

     PTF