Structure update + stronger Composer integration + better PSR-0 compatibility

I spent some time cleaning up parts of the project. Here's a rundown of the things I've changed/fixed.

* Removed submodule strategy. Composer now loads all dependencies. This is good for many reasons.
* Fixed namespaces in the test suite so that everything is PSR-0 compatible.
* Removed custom project autoloader. Uses standard Composer autoloader now.
* Test suite is now autoloaded by Composer.
* Turned amp.php into a real bash script using PHP env.
* Updated docs to reflect new installation procedure.

All tests passing - 4 tests being skipped. Not sure why.