Recursive Functions

Sorry for being late guys, but here we have the solutions for this chapter.

I have to finish the last 2 functions for the 6 exercise. I'll update as soon as possible. :heart: 

cc @fabioyamate @carlosgaldino
just to let you know about a different solution: https://github.com/carlosgaldino/programming-in-haskell/blob/d8441a3f2c131a0fb0c2f94e536c5fb3b5b4c211/ch06/Chapter6.hs#L106-L127