BUG: consistent subplot ax handling
CLN: Simplify Period construction / Resolution
Add some documentation on gotchas related to timezone library updates.
CI: update sqlalchemy to 0.9.6 in 3.4 build
Merge pull request #7607 from sinhrks/millireso

CLN: Simplify Period Construction / Resolution
Merge pull request #7391 from sinhrks/subplotax

BUG: inconsistent subplot ax handling
CI: change 2.7 build for sqlalchemy to 0.9.6
Merge pull request #7672 from rockg/holiday-doc

Add some documentation on gotchas related to pytz updates #7620
WIP: select_dtypes impl