add exercise pythagorean triplet

I hope I got the intent of this one.  I require two functions, one to solves the Project Euler problem of finding triplets with a specified perimeter and one from Ruby to generate triplets with sides within a range of values.

Other parts of the Ruby example seemed to be about doing something according to various conditions which might be specified.  You can kind of do something like this in Go with struct literals but I really didn't see the point of it in this context of Pythagorean triplets.

The test cases are easily solvable by brute force but certainly there is room for people to apply more advanced algorithms if they like.