R2py refactor

This works as before. You can just source the file and then run the same old "cat_items()" function to get (nearly?) identical output to what you got before.

I've tested it on the examples that were in the file and on many other simple regression things. It looks like it works pretty well. Since this is not user-facing and I've kept the ``cat_items()`` call constant, I don't think this needs in-depth review (though the code is pretty easy to read now).

Improvements:

* strict=TRUE argument in cat_index skips over contents that have to be converted to string using deparse().
* Improved README gives instructions/examples on use and installation
* More robust functions via exception handling (will likely spit-out *something* every time)
* S3 class instead of multi-if-then for content processing
* Yow! Paste-it! Cut down cat()-calls by 1000
* Better R packaging
* Roxygen2 for documentation (literate programming, yaddy-yadda)
* apply_functions() takes an object and applies a list of functions to it
* convert_items() returns pretty output as a string instead of printing to console as cat_items()