need to expose andThen in the tutorial
need to expose andThen in the tutorial

I kept getting `cannot find variable andThen` until I imported it from the Task module.
frankschmitt/elm-lang.org,jvoigtlaender/elm-lang.org,FranklinChen/elm-lang.org,amitaibu/elm-lang.org,frankschmitt/elm-lang.org,elm-guides/elm-lang.org,elm-guides/elm-lang.org,jvoigtlaender/elm-lang.org,amitaibu/elm-lang.org,FranklinChen/elm-lang.org