20x20 Extrusion Spool Rest for Cetus 3D

This was adapted from http://www.thingiverse.com/thing:43756. The majority of the script is credit to @jeremyalangreen

Added a rest area for a filament spool to sit on, specifically designed for the spool holder that comes with the Cetus 3D printer.

To generate the STL file, click the link to Open in Customizer. For the 20*20 extrusion used as the spool holder for the Cetus 3D printer, you can leave the default values as is, and it should provide a nice snug fit.