Ptero-- A Dactyl-inspired keyboard

Inspired by the [Dactyl keyboard](https://github.com/adereth/dactyl-keyboard), this keyboard is designed to be 3D printable by FFF printers. In Slic3r's estimations, this should print in 1/3 the time of the original-- one half can be printed in ~16hr instead of half of a half in ~24hr.

I also added the inboard 2U keys since I use them for Esc as well as the [ ] keys.

Depending on your slicer, you may need to enable thin wall detection in order to get this to slice correctly.

This is very much a work-in-progress: I have yet to print this left-hand test file and need to add holes for the cables as well as mounting points for the electronics.