Add bugsnag support

Hi, I added support for Bugsnag webhook :)

> [Available Plugins - Bugsnag](https://bugsnag.com/docs/notification-plugins)

![ss 2014-10-14 at 23 57 49](https://cloud.githubusercontent.com/assets/1041857/4631043/818aaa94-53b2-11e4-8371-0a23090bd848.png)