Single piece, quick-change spool holder and filament guide for Prusa i3 mk2

**This design has a few problems - I now have a new filament holder that is similar but holds two reels at a time for quicker changing (and is still nicer even if you only need to hold one reel) - see: http://www.thingiverse.com/thing:1847716 **

The least favourite part of my stock i3mk 2 is the filament holder, so I designed a new one. Should work too with any similar 6mm-frame printer.

Print as a single piece and clip to frame. To change the filament, simply pick up the old spool, and pl