TST: Tests and fix for unhandled data types in Excel writers.

Added tests and a fix for unhandled numpy data types in the
Excel writers. Issue #3122.
inlined some functions and avoid repeated conversion factor calculation when using period_asfreq_arr in period.c
BUG/TST: Test filter corner cases, and treat NaN as False.
BUG: Bug in loc setting with multiple indexers and a rhs of a Series that needs
     broadcasting (GH5206)
Merge pull request #5210 from jreback/loc_index

BUG: Bug in loc setting with multiple indexers and a rhs of a Series that needs broadcasting (GH5206)
Merge branch 'c_inline' of https://github.com/wuan/pandas into wuan-c_inline
Merge pull request #5096 from danielballan/filter-len-test

TST: Groupby filter tests involved len, closing #4447
CLN/BUG: Better validation of levels/labels/names
Merge pull request #5122 from jmcnamara/tst_excel_types

TST: Tests and fix for unhandled data types in Excel writers.
Merge pull request #5209 from jtratner/validate-everything-on-mi

CLN/BUG: Better validation of levels/labels/names