Changes on Pythagorean Triplets tests and exercise description

[LukeDias42]

I've recently done this exercise, I did this after completing the one it is based, on Project Euler. I found it a bit confusing that I must return with the Pythagorean triplets in ascending order by a, therefore I changed the tests to allow the users to send their answers in any order. Also, I think Project Euler has a shorter and a little clearer (at least to me) explanation of what the triplets are.