Add Semigroupal typeclass

[ersin-ertan]

A typeclass that allows combining independent contexts of F<A> and F<B>
Using Semigroupal<F> you form F<Tuple2<A,B>>
The primary method is: fun <A,B>product(fa:F<A>, fb:F<B>):F<Tuple2<A,B>>

P.S. using Tuple2 instead of Pair right?

[BranislavLazic]

What's the state of this issue?
Also, I think that correct signature of product method should be:
fun <A, B> Kind<F, A>.product(fb: Kind<F, B>): Kind<F, Tuple2<A, B>>

[ersin-ertan]

The state is no assignees, please feel free. Yes I believe so, in Arrow the Kind extension method will be used.