Isolate connection expressions.

- When requiring gabby.rabbit, don't automatically connect to XMPP and AMQP server.
Make core more functional.

I'm looking for a way to expose the Smack API less: people that use Gabby should be working with functions and data, not objects.  So far, the only exception to this is the underlying connection to the XMPP server.
Ignore credentials.
Remove redundant example.
Overhaul gabby's core.

- Reduce exposure of underlying dependencies.
- Improve documentation.
- Implement "recording" conversations.