iterateeIoEnumeratorToChunkerator has multiple implementation issues

[sullivan-]

Current implementation limitations:

• requires a Bimonad instead of just a Monad. I'm not sure if this is negotiable or not. It seems like we need to call F.extract on the iteratee to get it to "run".
• Uses promises for communication between producer and consumer. Maybe this is okay for, say, and Play converter. But there has to be a more catsy way to do this. Right now, my cat-fu is not strong enough to pull it off. Maybe in the future, I will figure it out. But if you are good with this kind of thing and want to take a stab at it, that would be great.
• Steals a Future from the global execution context to kick off the producer asynchronously. A more catsy approach, as described in the last bullet point, should do away with this. I didn't want to add an implicit ExecutionContext argument here, as that seems like an implementation detail, and a rewrite of this method without it would not be backwards compatible. Maybe there is some way to pull this off with Task? I tried, couldn't figure it out

[sullivan-]

I'd like to mention that I myself am only using this adapter in a test suite, so getting a better implementation here may well be a lot more important to you than it is to me. Of course, I want to see this project beautiful and complete. But I have a lot of priorities to balance. If you care, please consider chipping in! Thank you.