rev-2 (partial-rewrite)

This branch is currently under development, and all parts are subject to change. I'll do my very best to keep the latest commit working properly though.

Pull requests will almost certainly not be accepted for this branch at this time.
Sorry... It's a bit hard to explain exactly why... But perhaps it will be understandable if I just say that I've been working on this project for quite a long time now, and at this point rev-2 is kind of my baby. Until it grows up, and I send it out into the real world by moving it to the master branch, I feel very protective of it.

Notes:

• Gyuri Horak implemented NKRO and mouse keys in [his branch] (https://github.com/dyuri/ergodox-firmware) of rev-2. Not merged, but I plan to implement the features later, if I can. See [Pull Request #28] (https://github.com/benblazak/ergodox-firmware/pull/28).