Flexible filament guide for CraftUnique Craftbot

This is a "snap in" guide to allow the use of flexible filament (Ninjaflex, Filaflex, etc..) with the CraftUnique Craftbot. This unit fills the gap between the top of the thermal tube and the feed/idler wheels. That constrains the filament so that it has less of an opportunity to buckle and deform during the extrusion process. It mimics the filament guide used on other printers such as the Makerbot R2X.