Guilds

I've finally "completed" the guilds. There is probably a few bugs, and for sure there is still work to be done, but so far it seems to work.

The functionnalities are detailed in the wiki of my fork: https://github.com/lzbk/BrowserQuest/wiki/Guilds

If you want to test the functionnality before merging, the prior commit on branch lzbk, still has lots of debug messages (and a few bugs).

As such the guild only provide a way to know if your friends are online and to talk to them even when you don't see them. But in the long run they could be more than that.

We could develop "guild achievements" (such as killing mobs at the same time in various parts of the map, helping each other, finding each other when beginning far apart, whatever…).

For now, I use the notification system for all guild related update, I'm thinking it would be better to add an "ethertalk" div that would provide a little bit of history to make interactions more fluids. Speaking of notification, they seem to work better under chrome than firefox, for some reason I could not grasp.

Got loads of other functionnalities ideas (not all linked to guilds), but one thing at a time. If people feel like testing this, please do.