Make library PSR-0, -1, & -2 compliant

Niall,

Thanks for producing this great little library. We want to use it in our project, but wanted autoloader and composer support, so I added them. Here is a high-level summary:

* Moved and namespaced files for PSR-0, -1 and -2 support
* Added a composer definition file
* Added some very basic phpunit tests based on your documentation
* Added a backward compatibility layer with a deprecation warning

I tried the separate these into distinct commits so you could decide which features you wanted to merge in. If there are any changes to these commits that you'd like me to make, please don't hesitate to ask.

With sincerest thanks,

-Loren Osborn