Improved Y-Belt Clip

My MakerBot's Y-belt sometimes slips loose of the clip provided in the kit, so I designed a fix for it.

This hasn't been tested in situ yet, but I'm pretty confident that the underhang design will put the belt slipping issue to bed. Tuck the hook under the y-stage with the belt between the main bar and the ribs, and the screw should now be effectively applying pressure at *both* ends of the belt, as well as physically blocking it from moving down.

Getting that hole to print is annoying bu