iPhone 5s macro lens mount

This was inspired by [lens42's macro lens mount](http://www.shapeways.com/model/864992/iphone-5-and-iphone-5s-macro-lens.html) on Shapeways. The designer of that mount tracked down a cheap ($4) [lens from surplusshed.com](http://www.surplusshed.com/pages/item/l4471.html) that is suitable for iPhone macro photography. I wanted a mount that would slip over a case, and that I could print myself.
This version takes the mount design from my [loupe mount](http://www.thingiverse.com/thing:283545) an