*IMPORTANT* Updated CONTRIBUTE.md

I've been playing around a lot more with the tools available to us using
version control. Basically, I've updated the CONTRIBUTE.md with a basic
guideline on how to use branches and also how to solve merge conflicts.
Don't get me wrong, our system to carefully update our own files is THE
BEST PREVENTATIVE MEDICINE, but in case of issues, these instructions
should help. See me if you want a more in-depth explanation or some help
=D.
-Travis