Add a release checklist.
Add a release checklist.

I always forget things, this is good documentation, and it's been
helpful with the opus releases.

svn path=/trunk/vorbis/; revision=19461

mwgoldsmith/vorbis,ShiftMediaProject/vorbis,ksophocleous/vorbis,erikd/vorbis,nicolaichuk/vorbis,eidy/vorbis,eidy/vorbis,felipebetancur/vorbis,emscripten-ports/Vorbis,nicolaichuk/vorbis,ShiftMediaProject/vorbis,emscripten-ports/Vorbis,youfearm3/vorbis,youfearm3/vorbis,youfearm3/vorbis,eidy/vorbis,felipebetancur/vorbis,erikd/vorbis,ksophocleous/vorbis,mwgoldsmith/vorbis,felipebetancur/vorbis,ShiftMediaProject/vorbis,erikd/vorbis,nicolaichuk/vorbis,felipebetancur/vorbis,eidy/vorbis,mwgoldsmith/vorbis,ksophocleous/vorbis,emscripten-ports/Vorbis,nicolaichuk/vorbis,youfearm3/vorbis,ksophocleous/vorbis,ShiftMediaProject/vorbis,emscripten-ports/Vorbis,erikd/vorbis,mwgoldsmith/vorbis,ShiftMediaProject/vorbis,ShiftMediaProject/vorbis