Use `as` pattern for better efficiency in haskell.
Add straight to the point tiny haskell version.

I do know I shouldn't be using explicit recursion here. Yet, this seems
like a oddly somewhat hard problem to solve using this stupid algorithm.

I thought something like `groupBy` would be able to solve my problem by
grouping the chunks to be summed/subtracted together, but that turned
our to be pretty deviating.

In the end my `RomanNum` type was completely pointless, making the tiny
implementation better IMHO.

This is just for demoing porpoises, so it honestly doesn't matter much.