Itty Bitty Belted Extruder

**Update**: A hardware kit is available [here](http://clough42.com/go/product/itty-bitty-belted-extruder-drive-kit)

This is a lightweight belted extruder derived from the geometry of Greg Frost's excellent hinged accessible extruder.
Design elements:
1. NEMA 14 motor. This reduces the moving mass to about half that of a standard NEMA 17-based extruder.
2. GT2 (2mm pitch) belt drive. The belt is efficient and quiet. It eliminates the clicking noises that printed gears make (the real reason I started this project). The belt should also have a longer wear life than printed gears. This means that it requires a small GT2 pulley and belt, but the large pulley can be printed.
3. Standard Greg's Accessible Extruder geometry. The overall frame is shorter than the GAE, but I elected to retain the 608 bearings, 8mm bolt and Greg Frost's excellent guidler.
4. Additional frame structures to completely capture the hobbed bolt bearings. This allows the frame to hold the