rfc: Additions to Data.Either (take 2)

[Tobias Florek]

thanks joão for the write-up.

 > Proposal 1:
 > Add no new code, but document Data.Either to mention how to use `left`
 > and (+++) from Control.Arrow

(+1 for documentation, but that's not what that proposal is about)

 > Proposal 2:
 > Document Control.Arrow to exemplify the (->) instance usage.

+1

 > Proposal 7:
 > Don't implement mapRight, but include documentation in Data.Either
 > stating that it is just fmap.

+1

 > Proposal 8:
 > Bring bifunctors to base.

(my favorite by far)
+1

all others i am ignorant about.

cheers,
  tobias florek