Testing basic functionality of WI.EventListener.

Connecting the listener.
Invoked callback for kaboom event.
Invoked callback for kaboom event.
Disconnecting the listener.
Connecting the listener.
Invoked callback for kaboom event.
Disconnecting the listener.
Connecting the listener.
Disconnecting the listener.
Connecting the single-fire listener.
Invoked callback for kaboom event.
Disconnecting the single-fire listener.
Invoked callback for kaboom event.