[MSE] Spec updated to object-oriented API

Hi,

I just wanted to let people know that I have just published an updated
version of the Media Source Extensions
spec<http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html>.
This new version contains the object-oriented API we have discussed on the
list. I chose to go with a simple translation of the API for now and did
not introduce new methods like appendUrl() as originally proposed.

Summary of Changes:
- Map v0.5 methods into MediaSource & SourceBuffer objects and updated
example code.
- Updated all algorithm and event text to match the new objects and how
they interact.
- Converted the enumerations to the new string constant style.
- Updated API graphic to show the JavaScript/HTMLMediaElement boundary and
straightened some arrows.
- Introduced MediaSource.activeSourceBuffers attribute to make it easier
for applications to determine what source buffers are associated with the
enabled/selected tracks.
- Added TextTrack language in various places since it was overlooked in the
original spec.
- Removed open issues section since they are all captured in bugs.

I am really happy with how this new version turned out. I think this
object-oriented approach makes things easier to understand and provides a
better starting point for addressing some of the remaining open bugs.

Please let me know if you have any questions or comments.

Aaron