Fix behavior event collision

When a view has multiple behaviors, each with an event, the first behaviors event is not triggered.

In this case, the view, and dropdown click handlers are triggered, but the tooltip handler is missed.

```js
 V = Marionette.ItemView.extend({
   template: _.template(""),
   events: {
     "click": viewSpy
   },
   behaviors: {
     ToolTip: {},
     DropDown: {},
   }
 });

Tooltip = Behavior.extend({
   events: {
     "click": tooltipSpy
   },
});

DropDown = Behavior.extend({
   events: {
     "click": dropdownSpy
   },
});
```