code: function( callback ) {
              var me = this;
              var count = 0;
              this.keys(function( keys ) {
                  if ( !keys.length ) {
                      if ( callback ) me.lambda( callback ).call( me );
                  } else {
                      for ( var i = 0, il = keys.length; i < il; i++ ) {
                          me.remove( keys[i], function() {
                              count++;
                              if ( count === il && callback ) {
                                  me.lambda( callback ).call( me );
                              }
                          });
                      }
                  }
              });
              return this;
          }
docs: destroy everything