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)
* is_empty(string)
* is_null_or_empty(string)
* is_null_or_whitespace(string)
* equals(this, that, ignore_case=false)
* starts_with(string, start, ignore_case=false)
* ends_with(string, end, ignore_case=false)
* reverse(string)
* trim(string)
* parse_int(string, base)
* parse_float(string)
* tokenize(string, index)
* join(strings, delimiter)
* split(string, seperator=" ", ignore_case = false)
* index_of(string, goal, ignore_case=false, regex=false)
* conta