Automates gerber generation / renaming for the fab

I like to track the gerbers in the repo... but it strikes me that it may be better to host the zip files instead... Hopefully you can pick-and-choose the commits you like.

There are three ways to go, RE: gerbers. 
 1. We can just host the (entirely automated) script to generate them (and the oshpark zipfiles).
 2. We can host the gerbers, remembering to run the generate gerbers script before comitting changes to the repo.
 3. We can track the zipfiles directly in leiu of or in addition to the gerber files.

My intuition is that some of our target demographic couldn't be bothered to install pcb and run the shell script. Maybe it'd be best for adoption to track the zip files. If you accept all the commits, the repo will track gerbers and zipfiles; leave out the last commit and zip files won't be tracked. If you leave out af3f983216fa82aeb9c0f908f7b1c5625a135fbd, the gerbers aren't tracked.

My updates also change the pcb file version. If I read the file correctly, the version you initially used should have no trouble reading/editing the new pcb file format. You may want to clone my repo first and make sure everything looks alright.