Support for errbit

I tried using this with [errbit](https://github.com/errbit/errbit) and it had issues because it expects an API version to be sent. 

So I made it send a version number along with the request, I am not sure if 2.3 was the correct version but it was one accepted by errbit and it all seems to work now. Its only a tiny modification but it might be useful for anyone trying to use this with errbit (and possibly anything else that uses the airbrake API) 
I am not sure if this causes any issues with Airbrake but I would assume it doesn't.