Tool clip for Da Vinci 1.0a print head

This is a clip for mounting tools like this [pen holder](http://www.thingiverse.com/thing:1873991) to the stock Da Vinci 1.0a (probably 1.0 will work, too) print head. I used it to turn the Da Vinci into a plotter. The clip mounts very quickly.

The OpenSCAD file generates screw holes or, if you send the mounting bump diameter to 8.5, mounting holes (circle+square) meant to mesh with the ones in the pen holder (well, a little filing was needed), which I then welded to the tool clip with ABS sl