Proposal: Make Semigroup as a superclass of Monoid

[Marcin Mrotek]

>aside from the fact that it is an experiment that isn't part of the compiler or the language that we have, and uses assumptions about the way numbers work that don't hold for the ones we have

Just to throw in my two cents: LiquidHaskell seems to like something
that could be eventually wired into GHC with compiler plugins.

Best regards,
Marcin Mrotek