Open edge spool holder for Prusa i3 MK2

Spool holder where spool can be easily inserted from one side. Supports narrow and wide spools.

This design is remix of original Prusa i3 MK2 spool holder and this http://www.thingiverse.com/thing:1660600.

Its advisable to screw parts together with long (~4 mm diameter) wood screw. Screw also providers horizontal support ensuring rigidity in long run.

Use supports when printing part2.