Fully integrate composer

This PR makes it so Kohana modules must be installed using composer instead of using git submodules. 

Modules with the composer type of "kohana-module" are forced to be installed into the standard vendor directory.
I'm considering updating koharness to fetch the appropriate kohana/kohana bootstrap rather than having a separate copy. Also updating unittest so it also doesn't need its own bootstrap. I still want to keep koharness free of any phpunit-specific dependencies.