Fixed uses where observers where never unregistered

[chrisdp]

Fix to address #4

The root issue was that:

1. we would never stop watching completed promises meaning re-use of completed promise within a given component/main source could fire more than once.
2. when initially registering observers we would not un-register any existing ones leading to more then one being added per given component/source scope when using the same promise more then once in that scope.

Also added a small change to unobserve the delay timers so as to free up the observer memory in the background once completed as well.