public function add_type($type, $path = null)
	{
		isset($this->_asset_paths[$type]) or $this->_asset_paths[$type] = array();
		isset($this->_path_folders[$type]) or $this->_path_folders[$type] = $type.'/';

		if ( ! is_null($path))
		{
			$path = $this->_unify_path($path);
			$this->_asset_paths[$type][] = $path;
		}

		return $this;
	}