code: function cleanURL (URL, queueItem) {
      return URL
          .replace(/^(?:\s*href|\s*src)\s*=+\s*/i, "")
          .replace(/^\s*/, "")
          .replace(/^(['"])(.*)\1$/, "$2")
          .replace(/^url\((.*)\)/i, "$1")
          .replace(/^javascript:\s*(\w*\(['"](.*)['"]\))*.*/i, "$2")
          .replace(/^(['"])(.*)\1$/, "$2")
          .replace(/^\((.*)\)$/, "$1")
          .replace(/^\/\//, queueItem.protocol + "://")
          .replace(/&amp;/gi, "&")
          .replace(/&#38;/gi, "&")
          .replace(/&#x00026;/gi, "&")
          .replace(/&#x2f;/gi, "/")
          .split("#")
          .shift()
          .trim();
  }
docs: Performs string replace operations on a URL string. Eg. removes HTML
  attribute fluff around actual URL, replaces leading "//" with absolute
  protocol etc.
  @private
  @param  {String} URL          The URL to be cleaned
  @param  {QueueItem} queueItem The queue item representing the resource where this URL was discovered
  @return {String}              Returns the cleaned URL