The XMPPConnection class now has wrapper for del_event_handler method of ClientXMPP class.
Basis for extension of testing backend for presence.
Added presence related method stubs to base plugin class.
Ignoring some file types.
Added the handler stubs to base backend and callback methods to ErrBot class.
Added basic Presence class for backends with minimal interface.
Added stubs for event methods to xmpp backend, registered the handlers.
Merge pull request #244 from apophys/presence_poc

Presence plugin