Now that cdnjs is mirroring the beta files, we know what the final
locations are going to be. These identifiers will need to be updated
during the release process, just like all of the others.
This closes https://github.com/select2/select2/issues/2955.
Now Select2 can fire jQuery events that will match the corresponding
internal events. The `open` and `close` events are now publicly
accessible.
The selection adapter was chosen because it is the least likely to
be moved, but handles the most common events. This `EventRelay`
decorator should theoretically be able to decorate any of the
adapters, as they all have the `bind` method that it needs.
