Imperial Arduino Mega Standoffs

I was at Home Depot the other day looking fruitlessly for 4-40 standoffs to mount my Arduino Mega to my Prusa i3 and realized I could just print my own! These use 4-40 screws and you can adjust the height in the scad file if necessary. These are relatively low profile at only 4mm tall, but they stand the board off just the right amount.

Based on: http://www.thingiverse.com/thing:45447, but I fixed some things that weren't quite right and also increased the $fn variable since these are small parts and they weren't round anymore.