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
API: Raise on ``iloc`` indexing with a mask boolean that is not an ndarray (GH3631_)

     PTF

TST: added @snth test harness

DOC: doc updates for release notes,indxing.rst and v0.11.1
CLN: added NotImplementedError when trying to iloc with a mask that has an integer index

     (rather than ValueError)