If we let videojs auto-init the video/audio tags present in the page - we cannot guarantee that the
youtube library will be loaded by the time video.js is processing the tag.
Video.js uses the presence of a data-setup attibute to signal that it should auto-init this tag, so
we have to rename our config attribute to something else.
The videojs javascript is over 1MB of javascript which we don't need to
load on every page, now that we only require it demand, the js can be
lazily loaded when its needed, which keeps the first.js smaller and more
likely to stay in browser cache.
Marina Glancy