Exercises for the second chapter.

These are the exercises for the second chapter :smiley: 

Even this chapter being small, we could see some build in functions that Haskell provides to apply on lists. I spent a considerable time on the last two exercises, but then I started using [Hoogle] [1] which helped a lot :fireworks:.

@fabioyamate could you take a look?

  [1]: http://www.haskell.org/hoogle/
this one is wrong, we both missed the fix https://github.com/carlosgaldino/programming-in-haskell/pull/2#discussion-diff-14675783R4