Description: create Fizz-Buzz algorithm by Test driven development
Divisibility by 3 return 'Fizz'
Divisibility by 5 return 'Buzz'
Divisibility by 3,5 return 'Fizz-Buzz'
the rest return input

Test:  $ phpunit TestFizzBuzzTdd.php
Usage: $ php exec-Fizz-Buzz.php