improve unification of Of types (e.g. Of<In->B, A> with Of<A->In, B>, support Of types like Of<In->B, A>
fixed comments
Merge pull request #4 from frabbit/of_in_patch5

support unification of Of types like Of<In->B, A> with A->B in both directions, support unification of Of types (e.g. Of<In->B, A> with Of<A->In, B> in both directions