title: Do we need to unsubscribe from observable that completes/errors-out?
body: <p>When I know that the observable will definitely complete (either with <code>complete</code> or an <code>error</code> notification) <em>before</em> my component/class goes out of scope, do I still need to unsubscribe from it to prevent memory leaks? In other words, is completed/error-ed observable cleaned-up automagically so I don't have to worry?</p>