Solution for the first exercise.
Solution for the second exercise.
Solution for the third exercise.
Solution for the fourth exercise.
Solution for the fifth exercise.
Solution for the sixth exercise.
Solution for the seventh exercise.
Solution for the eighth exercise.
No need for list comprehension here.
Add missing functions for this answer.

Thanks @fabioyamate
Merge pull request #5 from laurocaetano/ch-05

Chapter 5 - List comprehensions