code: function (name, handler, options) {
              if (handler) {
                  var _handlers = this.__handlers__;
                  var _listeners = _handlers[name] = _handlers[name] || [];
  
                  _listeners[0] = zn.extend({
                      owner: this,
                      handler: handler
                  }, options);
              }
  
              return this;
          }
docs: Add a single event handler.
  @method upon
  @param name {String}
  @param handler {Function}
  @param [options] {Object}