Exceptions

Created by: deanpcmad

Hey, I've wanted for feature for a while and I finally had a bit of time to work on it.

This feature adds Exception logging, from the Airbrake client, into GitLab. The code is fairly basic at the moment as I have copied most of it from an app I built which has been tested.

It still needs a bit of work done and I need to just write some tests for it but I wanted to see what people thought about it first. Thanks!