use `Chat.type` in <message/>'s type attr in Send()
use `Chat.type` in <message/>'s type attr in Send()

Otherwise client.Send(..) cannot be used for MUC 'groupchat' messages.
This might break code, if you're not setting `Chat`'s type slot and rely
on `client.Send` set it to 'chat' by default

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