Small Fixes and SBT compatibility

Hi there,

I emailed you earlier. I made a couple small changes to the code. One was to fix a warning. Another was to make it easier to set a callback on a message listener. And most importantly, I made it possible to use the project as a dependency alongside SBT.

Also, I accidentally re-encoded everything in UNIX line endings. And at the moment I cannot remember for the life of me how to fix that. Apparently unix2dos is not installed on my workstation for some god forsaken reason.