Update version of node-xmpp defined in package.json - Fixes #121

Fixes this error (which stops hubot from starting up):
```
[Tue Oct 15 2013 21:39:42 GMT-0700 (PDT)] INFO Connecting HipChat adapter...

/Users/anonymous/codes/projects/hubot/node_modules/hubot-hipchat/node_modules/node-xmpp/lib/xmpp/connection.js:277
    this.socket.end();
                ^
TypeError: Cannot call method 'end' of undefined
  at Client.Connection.onEnd (/Users/anonymous/codes/projects/hubot/node_modules/hubot-hipchat/node_modules/node-xmpp/lib/xmpp/connection.js:277:17)
  at CleartextStream.<anonymous> (/Users/anonymous/codes/projects/hubot/node_modules/hubot-hipchat/node_modules/node-xmpp/lib/xmpp/connection.js:56:14)
  at CleartextStream.EventEmitter.emit (events.js:117:20)
  at _stream_readable.js:920:16
  at process._tickCallback (node.js:415:13)
```