Move python code to python dir
Add ruby implementation of stock passing some tests

It looks like any simple case with increasing prices overall will be
handled.
Test case where highest sell price is not the best
Reverse order of MiniTest includes

This silences a warning in some versions of MiniTest
Return [0, 0] for empty case instead of nil
Add test where neither highest nor lowest price is best
Improve and clarify solution

It passes all tests now and is fairly easy to read