Require a Monoid if the method is called xxxMonoid
Make fold1Monoid, foldSemigroup, and reduceMonoid an alias for reduceSemigroup
Require a Monoid if the name contains Monoid
reduceMap and scan1Map require only a Semigroup
Merge pull request #111 from fthomas/docfix

Require a Monoid if a method is called xxxMonoid