Adds category typeclass with hask instance

[neutropolis]

Adds Category as a typeclass with an instance for Hask (functions and types). As a consequence, laws can be defined now in a general way.

[neutropolis]

Now, you should be able to use generic laws to test particular instances. I recommend you to read about typeclasses (Functor, Eq, etc.) to understand what is going on in this code. I hope this serves you! 😉

[elbaulp]

I've made a mess mergin this PR. I want to merge it to a different branch than master, to keep it for a future improve (as I learn more CT and understand better what this code does)

Would you mind if I left this PR as it is? or could you try to make the PR to category-improved branch?

Bests, and thank you.

[neutropolis]

Of course, use it at your best convenience! Feel free to ignore (or even close) this.

[elbaulp]

No, I won't ignore it nor close it, By the time I am able to understand it fully I will merge it. Bests