TST: PeriodIndex pickle roundtrip does not recreate freq GH2891
BUG: PeriodIndex pickle roundtrip does not recreate freq GH2891
Merge pull request #3224 from y-p/GH2891

PeriodIndex pickle roundtrip does not recreate freq GH2891
DOC: update RELEASE.rst
BLD: Compact builds to fit into travis's 5-job concurrency limit
DOC: update CONTRIBUTING.md
BUG: GH3216 Upcast when needed to DataFrame when setitem with indexer
ENH: On a mixed DataFrame, allow setting with indexers with ndarray/DataFrame on rhs