TTML2 Latest Editor's Draft

Since the gh-pages branch of the ttml2 repository [1] no longer represent
the Latest Editor's Draft, but instead represents some form of a Working
Group Consensus Draft, I have created a new branch ed-master [2], where I
will do my editing, and which represents the Latest Editor's Draft, which
URL has been updated to [3].

I suggest that the copy of ttml2.html found in the gh-pages branch [4],
have its Latest Editor's Draft link updated to point at [3] as well, since
gh-pages no longer serves as the home for the Latest Editor's Draft, and
is, therefore, misleading since it is also presently labeled as Editor's
Draft.

[1] https://github.com/w3c/ttml2
[2] https://github.com/w3c/ttml2/commits/ed-master
[3] https://rawgit.com/w3c/ttml2/ed-master/spec/ttml2.html
[4] https://rawgit.com/w3c/ttml2/gh-pages/spec/ttml2.html