[opus] Opus Todo

[Timothy B. Terriberry]

Ralph Giles wrote:
> It looks like this was done a couple of years ago, primarily in commit
> e9bbfacf0a1bbade70005fa730cc50e838baaa32, and part of the 0.2 release.
> I don't know if there's any useful follow-up work to be done.

I think the biggest gap at the moment is the ability to edit metadata 
(i.e., the Opus equivalent of something like vorbiscomment from 
vorbis-tools).