Cleaned up a bunch.  Added disable_autoload.  Nicer fatal errors now!

- Both outputted errors and comments were cleaned up.
- A disable_autoload key was added to config which will cause lab to register an
autoloader that throws an exception when trying to load a class.  This is set to TRUE
by default.
- The normal arbitrary config data has been moved to an internal 'data' key on the
array, and it and it alone is passed to the callback, so you cannot get tests dir or
other config information, only arbitrary data.