FizzBuzz kata used to learn the Open/Closed SOLID principle.
First commit (472d7d3) has a not OO solution for FizzBuzz kata.
Third commit (99e83e8) has an object oriented version.
Last commit (ee9df1d) has an OO version using the visitor pattern to achieve the open to extend, closed to modify principle, added the wook rule (numbers divisible by 7).