BUG: use size attribute (not method call)
BUG: force float64 dtype in object results for groupby
BUG: unstack fails in PeriodIndex
Merge pull request #7089 from cpcloud/groupby-size-windows-bug

BUG: use size attribute (not method call)
Merge pull request #7041 from sinhrks/unstack

BUG: unstack fails in PeriodIndex
release conflict
REGR: Regression in groupby.nth() for out-of-bounds indexers (GH6621)
Merge pull request #7094 from jreback/groupby_nth_repr

REGR: Regression in groupby.nth() for out-of-bounds indexers (GH6621)
BUG: Datetime values in DataFrame.quantile()

Closes #6965

previously returned nonsense
Merge pull request #7093 from TomAugspurger/quantile-datetime

BUG: Let DataFrame.quantile() handle datetime
BUG: tz info lost by set_index and reindex