v3.3.13

You guessed it, a load of awesome changes from contributors:

Thanks @friday for the following:

-   Captions fixes
-   Fix poster race conditions
-   Minor code improvements for quality switching
-   Minor event changes
-   Fix condition in events.toggleListener to allow non-elements
-   Suggestion: Remove array newline rule
-   Contributions improvements

-   fix: html5.cancelRequest not remove source tag correctly (thanks @a60814billy)
-   remove event listeners in destroy() (thanks @cky917)
-   Fix markdown in README (thanks @azu)
-   Some parts of the accessibility improvements outlined in sampotts#905 (more on the way...)
-   Fix for bug where volume slider didn't always show

Merge branch 'master' of github.com:sampotts/plyr

# Conflicts:
#	demo/dist/demo.css
#	dist/plyr.css
#	dist/plyr.js.map
#	dist/plyr.min.js
#	dist/plyr.min.js.map
#	dist/plyr.polyfilled.js.map
#	dist/plyr.polyfilled.min.js
#	dist/plyr.polyfilled.min.js.map

Merge branch 'develop'

Merge pull request sampotts#975 from sampotts/develop

v3.3.8