[nick_g]

I'm going to have to read through this again to really grasp it

I believe there's a minor error in the "Tensorful" section. When describing that `CaseTree` is a profunctor, the type of the contravariant map over `CaseTree` is written as `(i' -> i) -> CaseTree f i r -> CaseTree i' f r`. I believe the last term should be `CaseTree f i' r`