Chat invites support

Closes #260

commit 0af11b3aa988831be4960b7b8083dfcdade40ec0
Author: Ben Langfeld <ben@langfeld.me>
Date:   Thu Jun 26 16:38:09 2014 -0300

    Build

commit 8f18eeb6cdfc17bfe36e987451ddf710b1e901a8
Author: Melissa Noelle <melissamatara@gmail.com>
Date:   Tue Jun 17 17:22:43 2014 -0400

    Added event trigger for incoming chat invites.