Extruder Gear Case (for Bondtech)

*Update 2015-10-25: added a new version with the thread pitch fixed, and designed to use the threaded E3D bowden coupling as suggested by mkelley. This coupling holds better than the pressfit version and the tube is easier to detach than the metal fittings listed below.*

Redesigned to work with a different [pneumatic fitting](http://www.ebay.com/itm/221784682401?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) (I didn't like the bowden tube connection being the weakest part of the