[MSE] Spec Updates Published

I have posted more changes to the Media Source
Extensions<https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html>
 spec.

Summary of changes:
Bug 21327 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21327> -
Crossfade clarifications.
Bug 21334 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21334> -
Clarified seeking behavoir.
Bug 21326 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21326> - Add a
note stating some implementations may choose to add fades to/from silence.
Bug 21375 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21375> -
Clarified decode dependency removal.
Bug 21376 <https://www.w3.org/Bugs/Public/show_bug.cgi?id=21376> - Replace
100ms limit with 2x last frame duration limit.

Diffs:
https://dvcs.w3.org/hg/html-media/rev/f7f2b7226543

Aaron