0.21.1 backports (round 1)
Reminder: don't squash before merging.
@jreback @jorisvandenbossche the failure in https://travis-ci.org/pandas-dev/pandas/jobs/313729058 is our old friend, the clipboard failures, since https://github.com/pandas-dev/pandas/pull/17723 wasn't backported.

This should be good to go, and then I'll need to make sure I didn't miss any on this round. I'll merge later today. hmm i though i has a commit where i moves the clipboard tests

but oh well @TomAugspurger This can be merged? (the failure is a clipboard related, so I think can be ignored) Oh, yes. I thought I had.