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.
@lenton possibly this is what's causing the issue with SYSPATH during build - shouldn't this be defined relative to the index.php so that it's not dependent on the current working directory? eg `$vendor_path = __DIR__.'/vendor/'`