observer-util: Not accessing the changed property doesn't call observe second time

.observe() callback is not called if the changed property getter is not executed in the .observe() callback. Take a look at the example below. Execute it then try uncommenting the line and commenting the one above.

const observer = require('@risingstack/nx-observe');

const observable = observer.observable();

// This way doesn't call the callback twice
observer.observe(() => console.log(observable));

// This way works
// observer.observe(() => console.log(observable.value));

observable.value = 3;

setTimeout(() => observable.value = 4);