Deprecate Foldable for Either

[Francesco Ariis]

On Thu, Mar 02, 2017 at 05:19:26PM +0000, Oliver Charles wrote:
> Personally, I think it would be a shame to lose foldMap on EIther. I
> frequently foldMap over Maybe values (where mempty is suitable in case of
> "failure"), and I can certainly see myself doing the same thing with Either.

I am not trying to be polemic, just to see where the community
stands: regarding Either/Maybe: do you have use cases for length
(sum) too?