Changed VideoJS -> videojs in api.md

I think, it's the proper name of the component in the default set.
Merge pull request #585 from fluf1024/patch-1

Changed VideoJS -> videojs in api.md
Close GH-581: export Component.prototype.fadeIn/Out.
Adding line to CHANGELOG
Close GH-593: When autoplay = true, delete tag.poster instead of setting to null.
Adding line to CHANGELOG
Close GH-588: Export bufferedPercent.
Adding line to CHANGELOG
Fixed up some changelog issues