docs: function( url, data ) {
              data = data || {};
  
              //if there's forward history, wipe it
              if ( this.getNext() ) {
                  this.clearForward();
              }
  
              // if the hash is included in the data make sure the shape
              // is consistent for comparison
              if ( data.hash && data.hash.indexOf( "#" ) === -1) {
                  data.hash = "#" + data.hash;
              }
  
              data.url = url;
              this.stack.push( data );
              this.activeIndex = this.stack.length - 1;
          }