Partially apply FreeC

I am not sure if this is the best option, but making this change allows types defined using `FreeC` to be passed as a type parameter to something like `Natural`. For example, it allows for defining the natural transformation [todomvcN](https://github.com/purescript-contrib/purescript-angular/blob/b459f8b6a8ab3531591481dca9c62c57b7f86724/examples/TodomvcF/TodomvcI.purs#L38).