Upgrade to latest release of node-xmpp

node-expat was removed from dependencies because node-xmpp has it as a dependency already. I couldn't see it being used for anything else, so I removed it. Seems to work just fine.

Fixes #52. I mentioned having trouble, but that was because I was trying to do it with HEAD, instead of the latest release. Just upgrading to 0.10.0 doesn't seem to have been any trouble at all.