Make initial load seem more smooth

At current, when a user accesses JabbR, the page and scripts are loaded (5k), then the key combinations are loaded (<1k),  then the entire list of rooms (~105kb) is loaded, then the current room's contents are loaded (usually around 25kb), then each other room is loaded one at a time.

This change rearranges the load of things to be: your current tab then the lobby, other rooms (as a batch) and commands.  It makes things feel quite a bit faster, particularly down slow connections, even though we're not doing any less work.