TST/CLN: centralize module check funcs
BUG: df.reset_index loses tz
BUG: offsets.apply may return datetime
Merge pull request #7533 from sinhrks/resetindex

BUG: df.reset_index loses tz
Merge pull request #7451 from sinhrks/skiptest

TST/CLN: centralize module check funcs
Merge pull request #7502 from sinhrks/offsetret

BUG: offsets.apply may return datetime
TST: dtype test fixes for GH7533
GH 7512 - bug in expanding_{cov,corr} for objects of different lengths
fixed __flex_binary_moment() to deal with mismatched index sets
BUG: ewma() doesn't adjust weights properly for missing values
Merge branch 'ewma' of https://github.com/seth-p/pandas into ewma