Minor cleanup to MonoMonoid.
Minor cleanup to MonoMonoid and added product along with tests.
Added division and divisibility code to MonoMonoid along with tests.
More division code.
Removed unused code from PolyRing.
Removed unused code from PolyRing.
Added full support for comparison to MonoMonoid, along with module monomial and non-total-degree grading. Also forwarded compare from PolyRing to MonoMonoid.