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.
yeah, after reading the chapter, it seem trivial to do, I mean, more trivial than traditional loops