Remove Links Pointing to old GitHub Gitter repository

Something I noticed when I first started local development was a green DEV button at the top of the page. Clicking on it took me to https://github.com/troupe/gitter-webapp/tree/develop.

When I traced down this link in the code I noticed that there was one more reference to this old repository and I changed it too. All the other references to the old repository are in comments or in test descriptions.

I realize that this is not a requested change so there are 3 options:

1. close this MR (I'm not going to be upset because it didn't take much of my time)
2. merge only the first commit (0 risk, only string constant change)
3. merge both commits, the second one includes tiny code change (I did full text search of the codebase and replaced the only use of the method) I couldn't test it though because I don't have access to the beta environment.