String Theory, a string library for OpenSCAD

This library is a spin off of [Relativity](http://www.thingiverse.com/thing:349943), my other OpenSCAD library. I needed a string processing library for some more advanced features I wanted to implement, and since none were available to my liking I rolled my own.
The library includes the following functions:

* before(string, end)
* after(string, start)
* between(string, start, end)
* substring(string, start, length)
* upper(string)
* lower(string)
* title(string)
*