objects, it now has method names.
Added three methods, 'has_lib()', 'has_scripts()', and 'has_data()'
  to determine if we need to run each of the three possible sub-commands.
Added 'get_sub_commands()' to take care of finding the methods named
  in 'sub_commands', running them, and interpreting the results to
  build a list of sub-commands that actually have to be run.