Update languages.md

Spanish translations are not updated
Added doc for remaining time and removed onWaitEnd doc
Merge branch 'stable'
@mmcc fixed an issue where errors on source tags could get missed. closes #1575
@heff enhanced the event listener API to allow for auto-cleanup of listeners on other componenets and elements. closes #1588
@mmcc fixed an issue with the VolumeButton assuming it was vertical by default. closes #1592
@DevGavin added a Simplified Chinese translation. closes #1593
Updated instructions for issue 1596
Merge pull request #1598 from pascuals/patch-1

Update languages.md
Merge branch 'master' of https://github.com/videojs/video.js
Updated event listener for issue 1545