code: function(url, params, options) {
          var script = document.createElement('script');
          script.setAttribute("src", Ext.urlAppend(url, Ext.Object.toQueryString(params)));
          script.setAttribute("async", true);
          script.setAttribute("type", "text/javascript");
          return script;
      }
docs: Create the script tag given the specified url, params and options. The options
  parameter is passed to allow an override to access it.
  @private
  @param {String} url The url of the request
  @param {Object} params Any extra params to be sent
  @param {Object} options The object passed to {@link #request}.