Proposal: Allow Promise callbacks to be removed

[Oliver Dunk]

> What happens to `p2` if I "unthen" `f` from `p1`?

That’s an interesting point to explore. I would intuitively say p2 continues to exist, but is never resolved or rejected.

> Interesting. I have a proof of concept that would let you do this

Andrea, that’s pretty much exactly what I was thinking. I’m assuming there is no way to polyfill onto the actual .then and .catch methods?