code: function(input, options) {
          this.input = input;
  
          var selectivity = this;
          var inputListeners = this.options.inputListeners || Selectivity.InputListeners;
          inputListeners.forEach(function(listener) {
              listener(selectivity, input, options);
          });
  
          if (!options || options.search !== false) {
              input.addEventListener('keyup', function(event) {
                  if (!event.defaultPrevented) {
                      selectivity.search(event.target.value);
                  }
              });
          }
      }
docs: Initializes the input element.
  
  Sets the input property, invokes all input listeners and (by default) attaches the action of
  searching when something is typed.
  
  @param input Input element.
  @param options Optional options object. May contain the following property:
  search - If false, no event handlers are setup to initiate searching when the
  user types in the input field. This is useful if you want to use the
  input only to handle keyboard support.