AsyncObservable cannot return a value after previously resolving

[phillipskevin]

An AsyncObservable cannot return a value from its getter if resolve has already been called.

That means the observable below cannot be used to toggle from 0 to 1 and then back to 0:

	var asyncObs = new AsyncObservable(function(lastSet, resolve){
		if (value.get() === 1) {
			resolve(1);
		}

		return 0;
	});

[phillipskevin]

Maybe what is strange about this is that the value ever becomes 1, since even when you resolve(1) you also then return 0.