Don't show the favorite star button for people who can't join a room
I tried to favorite the https://gitter.im/Microsoft/VisualStudio room but it did not persist because I was signed in using my Twitter account and https://gitter.im/Microsoft/VisualStudio only allows Github users.
When you favorite a room, it tries to join you to the room if you haven't already. Which doesn't work for a Twitter user in a GitHub-only room.
Gitter shouldn't show the favorite star button for people who can't join a room.
Discussion on Gitter,