[MSE] Spec Updates Published

Adrian and I have published several updates to the Media Source
Extensions<https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html>
spec
in the last week.

Summary of changes:
Bug 21796 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21796> - Removed
issue box from 'Append Error' algorithm.
Bug 21703 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21703> - Changed
appendWindowEnd to 'unrestricted double'.
Bug 20760 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=20760> - Adding
MediaPlaybackQuality object.
Bug 21822 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21822> - Clarify
instances of 'fire ... event ... at the X attribute' text.
Bug 21819 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21819> - Remove
"compressed" from "Coded Frame" definition.

Diffs:
https://dvcs.w3.org/hg/html-media/rev/237133bfdd57  - Bugs 21796,  21703,
20760
https://dvcs.w3.org/hg/html-media/rev/5f5fdb05c2d2 - Bug 21822
https://dvcs.w3.org/hg/html-media/rev/3ec0a2703d1a - Bug 21822
https://dvcs.w3.org/hg/html-media/rev/ffb76048861e - Bug 21819

Aaron