Multiple fixes: old issue #548, current issues #754 and #902

In version 2.9, I reported issue #548, that controls hide when using keyboard to scrub even if the alwaysShowControls option is set to "true." Pull request #569 merged this fix, but did so in the /build directory. It appears that fix did not move forward with versions and the issue is occurring in the latest version. Adding fix in the /src directory so that future builds get the fix.

In browsing open issues, I found issue #754, which was also affecting me. Commenter marshallbu had a work-around that fixed the issue for me. I've added that fix to the /src and /build directories.

Added fix for issue #902 which hides the native captions that occur in Chrome in preference to the captions generated by mejs.