Shopbot CNC Pendant

I was inspired by [this CNC pendant](http://www.vistacnc.com/b07_pendant_P1/pendant_M1.htm), but I wanted to make one that I could hack on my own, add buttons, change functionality, and that I could guarantee would work well with my Shopbot.

The way this works is you plug it into your Shopbot controller computer, and enter "Keyboard Control Mode" in the control software. The red/green/blue buttons on the pendant change you into "X/Y/Z" axis mode. Then the jog wheel moves the machine. The jog wheel button puts you into "detail" mode, where each movement steps the machine by a much more precise amount.

Naturally, you could expand this, for example add a button for "jog" mode to move the machine faster, or add buttons to zero the X/Y/Z axes.

Here's a parts + tools list:
* 3D Printer (I use a Makerbot 5th Gen) + filament
* [Arduino Micro](https://www.adafruit.com/products/1315) - I used the "headerless" version and then soldered on some [0.1" female headers](https://www.adafru