Maybe type alias mismatch

[NeQuissimus]

https://github.com/scalaz/scalaz/pull/1827#discussion_r191635011

I had to remove a type annotation because otherwise the following type error would be thrown:

[tut] *** Error reported at /home/nequi/dev/scalaz/example/src/main/tut/ct/Functor.md:40
<console>:19: error: type mismatch;
 found   : scalaz.data.Maybe.Maybe[Long]
 required: scalaz.Prelude.Maybe[Long]
    (which expands to)  Option[Long]
       val x: Maybe[Long] = just(50L)
                                ^
scalaz.data.Maybe.Maybe[Long] <: scalaz.Prelude.Maybe[Long]?
false
[tut] *** Error reported at /home/nequi/dev/scalaz/example/src/main/tut/ct/Functor.md:41
<console>:20: error: not found: value x
       x.map(_ - 8L)

Somewhere the type aliases for Maybe don't line up and I cannot figure out how to fix it. It would be appreciated if somebody took a look and put the type annotation in examples that #1827 removed back.