Make it simpler to run the tests.

Fix the limitation where tests can only be run if the current directory where the codingstandards are checked out is called 'CakePHP'. Instead any directory that can also be used in a classname will work.

The eval bits are hacky has hell but avoid even more strange practices like storing each sniff twice or having totally crazy file layout to facilitate tests.

I've also removed the need to call exec() which I consider a tradeoff vs. having to use eval().