PubSub protocol support (#142)

* PubSub protocol support
Added support for :
- XEP-0050   (Command))
- XEP-0060   (PubSub)
- XEP-0004   (Forms)

Fixed the NewClient function by adding parsing of the domain from the JID if no domain is provided in transport config.
Updated xmpp_jukebox example

* Delete useless pubsub errors

* README.md update
Fixed import in echo example

* Typo

* Fixed raw send on client example

* Fixed jukebox example and added a README.md

tcp_server_mock.go

@@ -280,7 +280,7 @@ func bind(t *testing.T, sc *ServerConn) {
   	<jid>%s</jid>
   </bind>
 </iq>`
-		fmt.Fprintf(sc.connection, result, iq.Id, "test@localhost/test") // TODO use real JID
+		fmt.Fprintf(sc.connection, result, iq.Id, "test@localhost/test") // TODO use real Jid
 	}
 }