Fix a link in the documentation for Traverse (#3383)

* Correct some mistakes in Comonad documentatoin

* Fix link in traverse doc

docs/src/main/tut/typeclasses/traverse.md

@@ -160,7 +160,7 @@ def foldMap[F[_]: Traverse, A, B: Monoid](fa: F[A])(f: A => B): B =
   Traverse[F].traverse[Const[B, *], A, B](fa)(a => Const(f(a))).getConst
 ```
 
-This works because `Const[B, *]` is an `Applicative` if `B` is a `Monoid`, as explained in [the documentation of `Const`](const.html#example-2-traverse).
+This works because `Const[B, *]` is an `Applicative` if `B` is a `Monoid`, as explained in [the documentation of `Const`](../datatypes/const.html#example-2-traverse).
 
 ## Further Reading