Minimal Raspberry Pi mount for Prusa i3

I'd started out by printing one of [MarkBenson's Pi Mounts](http://www.thingiverse.com/thing:79834) and then discovered my Pi was so old it didn't have the mounting holes.

Print out 4 of these and use some rubber bands (or steal your some hair elastic from your daughter) and you can mount your Pi with or without screw holes.