* check_stanza does not require stanza_class parameter. Introspection!
* check_message, check_iq, and check_presence removed -- use check
instead.
* stream_send_stanza, stream_send_message, stream_send_iq, and
stream_send_presence removed -- use send instead.
* Use recv instead of recv_message, recv_presence, etc.
* check_jid instead of check_JID
* stream_start may accept multi=True to return a new SleekTest instance
for testing multiple streams at once.
