Prusa i3 MK2 Spool Holder

UPDATE - v2 of nut and screw. Screw is 100mm long (vs 75) and both nut/screw have a slightly sharper angle for the taper.

"Remix" of quick change universal spool holder. Added supports for Prusa i3 MK2 - nothing more. Thanks to the great work of @Foreverwinter

http://www.thingiverse.com/thing:1241566