Nickname can be specified when joining MUC
Nickname can be specified when joining MUC

Client.JoinMUC now accept second argument as nickname.

ordbogen/go-xmpp,dullgiulio/go-xmpp,nb-titan/go-xmpp,Like-all/go-xmpp,mattn/go-xmpp,skiz/go-xmpp,eagafonov/go-xmpp,pranavraja/go-xmpp,titan-x/go-xmpp