Upgrade to match new Events

ParcelEvents should be an optional plugin.  It should not be included in every Parcel.  You should be able to do:

```js
var MyEventfulParcel = Parcel.subClass({
// ....
}).mergePrototype(Parcel.Event, true);
```
You can either merge them one by one or have two subclasses to inherit from, one eventful, one without events.