Update video.js to fix seeking and autoplay
Bump the required version of video.js up to 4.7.2 because the earlier version built the SWF for a version of Flash that had issues with appendBytes. Handle autoplay inside the tech itself because video.js support calls play before the Media Source has opened and the call ended up ignored. Fixes #112. Fixes #128.
Merge pull request #136 from videojs/feature/vjs-4.7.2

Update video.js to fix seeking and autoplay