Add Bugzilla integration

I'm not sure what would happen if the user typed wrong, for example, username in the "assigned-to" field. If that happens, Bugzilla returns an error. Also, in some places I `throw` errors. How safe is it?

![screenshot 2014-07-15 21 33 14](https://cloud.githubusercontent.com/assets/1079123/3594643/27d3d788-0ca3-11e4-8a80-223c2955c38b.png)

The node convention is to do: `callback(err)` if there's an error, and `callback(null, result)` if there's not an error.

If you actually throw an exception in normal node code then it crashes the entire process, which we don't want. (We avoid this problem in most of the rest of the event-worker by using promises, but this code is still "raw" node).