function readModuleArg() {
  const module = args.c ? 'material.components.' + args.c : (args.module || args.m);
  if (!module) {
    gutil.log('\nProvide a component argument via `-c`:',
      '\nExample: -c toast');
    gutil.log('\nOr provide a module argument via `--module` or `-m`.',
      '\nExample: --module=material.components.toast or -m material.components.dialog');
    throw new Error("Unable to read module arguments.");
  }
  return module;
}
@returns {string} module name. i.e. material.components.icon