Moved SleekTest to sleekxmpp.test.
Organized test suites by their focus.
- Suites focused on testing stanza objects are named test_stanza_X.py
- Suites focused on testing stream behavior are name test_stream_X.py
Updated XMLStream to return True or False from removeHandler to indicate if the handler
existed and was removed.
Waiter handlers now unregister themselves after timing out.
