Adding **kwargs passthrough to ClientXMPP and BaseXMPP constructors to

facilitate use of parent class kwargs (e.g. socket). This change was necessary for our use case in order to pass SleekXMPP a socket which had been negotiated from a websocket handshake (skipping the connect stage), at which point the client worked more or less perfectly. Other options to permit passing a socket into the ClientXMPP class are much deeper and more abiding hackery. The desired usage is as below:

    ws = websocket.create_connection("ws://192.168.0.15:8001/jabber")
    xmpp = sleekxmpp.ClientXMPP('user@localhost', 'password', socket=ws)

Thanks for the library!