ENH: add __ne__ method to period comparisons

BUG: fix in spare_frame for issue with running apply on a SparseFrame didn't
     allow the setting of the columns with a rename to work properly
     something broke this......
Merge pull request #3205 from jreback/tests_fix

TST: fix tests in master
CLN: refactor core/index and tseries/index,period to have their formats and to_native_types be consistent
     in naming / operation
ENH: add support for Period formatting (as a native type)
TST: add period support to makeCustomDataFrame for testing purposes
BUG/TST: format multi-index nan correctly
Merge pull request #3193 from jreback/index_fmt

CLN: refactor core/index and tseries/index,period to have their format, to_native_types methods consistent
BUG: automatic color cycling when plotting Series without style or color argument
Share color cycle between left and right axes
Add note in RELEASE.rst
Merge pull request #3207 from hayd/GH2836-resolve-merge-conflict

Gh2836 resolve merge conflict