function getRoot( dir ) {
	// Ensure that we do not enter a parent directory...
	dir = resolve( ROOT, dir );
	if ( dir.substring( 0, ROOT.length ) === ROOT ) {
		return dir;
	}
	return ROOT;
}
Returns a root directory from which to search for packages.

@private
@param {string} dir - directory
@returns {string} root directory from which to search