MNT : slight refactor of Axis.set_ticklabels

update both labels (top/bottom or left/right), even if
they are not both visible.
Merge branch 'travis_text_fixes'
Ignore NaN warnings in angle helper.

It it expected that the array may contain nan and this is handled correctly using nanmin
Filter invalid warning in calculation of theta
Filter warning in tight layout demo:
Reenable plots in tight layout demo
Remove leftover print
Merge pull request #3942 from tacaswell/axis_refactor

MNT : slight refactor of Axis.set_ticklabels
Correct Accepts string
Merge pull request #3954 from jenshnielsen/accepts_issue

DOC : Simplify set_boxstyle Accepts section of FancyBboxPatch
Merge remote-tracking branch 'jenshnielsen/travis_docs_deploy'
Merge remote-tracking branch 'jenshnielsen/travis_text_fixes'
Merge branch 'examples_warnings'