Made the Maybe types into a Monoid.
Made the Maybe types into a Monoid.

In order to use Maybe as a Monoid the value inside it must also be
monoids. This allows you to do things like:
	Just(9) + Just(10) == Just(19)
	Just("Hello ") + Just("World") == Just("Hello World")
	etc.

fnl/pymonad,KenetJervet/pymonad