ENH/BUG: partial string indexing with PeriodIndex
Merge pull request #7043 from sinhrks/pslice

ENH/BUG: partial string indexing with PeriodIndex
ENH nlargest and nsmallest Series methods
wip
WIP: use fused types
DOC/REF: add docstrings and DRY it up
ENH: use object in fused types to allow object array in cython
TST: test all numeric types used
CLN: factor out special cases
ERR/TST: raise on object dtype
CLN: remove special casing of object dtype since we disallow it