Added shorthand methods and 3rd Array args

I just realize that it would have been better to have a different order
in the array i.e. eventType first. However, I'd rather write [ true ]
than [ 'value', true, false ].
Some combinations won't be so common or allowed, so I think will do.
To be able to have a .once() ability would be very nice for online games
or large indexes of fast changing data, where you wouldn't wan't to
update every ms, but rather every few seconds.