groupBy not using lift #1085
Description
The current implementation of groupBy is no longer using lift. This actually muck with some other plans in the works for logging and debugging hooks.
GroupBy should be refactored to use lift.
If you look at it the GroupByObservable is really just a factory for a Subscriber. That's what we use Operator class for. I clearly didn't review this one very well when I merged it a long time ago. It seems that RefCountSubscription instance could be folded into the operator's subscriber as well.