Chapter 5: List comprehensions

@laurocaetano and @carlosgaldino Have good times reading the chapter and doing the exercises. Exercise 5 was quite challenge but I gave up, not sure if it is a proper answer for that :disappointed: 

Great stuff seeing LINQ relation to list comprehensions on Erik Meijer lecture.
How it would behave in this case: `encode 3 "Haskell is Fun"`? What will be the output?
`"Kdvnhoo lv Ixq"` or ``"kdvnhoo lv ixq"`?