Fix out of sync names in brain

I've been running this bot for a while and one of the things we've noticed is that @ messages to the bot inside muc no longer work if a user has changed their name. These changes will send a name as part of the presence events (was previously commented out) but as the last parameter. The brain name will only be updated if a name has been provided (I tested with another hipchat bot which has a null name on room join).