Better filament guide for Wanhao i3, Maker Select, etc.

This filament guide is a remix of the "updated" filament guide for the Wanhao i3. It was completely redesigned and has three major improvements: 1. The notch for the angled support for the spool holder is now the correct angle, so no manual modifications are necessary, 2. It has been shortened significantly, 3. The tolerances on the screw holes are now correct. You want the filament to be held as close to the location of the extruder as possible. Shortening the guide brings the filament closer t