RepRap Pro Mini extruder protector

## Who's it for?
Probably only useful for owners of the following design (or similar):
http://www.think3dprint3d.com/Kossel-Mini-3dPrinter-Kit

The Kossel mini kit I got from Think 3d Print 3d uses a RepRap Pro mini extruder on one upright beam with a feed from a filament reel mounted on one of the upper horizontal beams.

## Why's it needed?
When printing the filament was rubbing on the large gear of the extruder due to the tension between the reel and the extruder. This is probably b