Create a module for test cases

In such a large project, it's crucial that each class is tested as soon
as possible. Before now, each Game State module could only be tested
after the Game State class was completed, resulting in many untested
component classes.

test.py provides a simplified game loop that allows you to declare a
class object as a global, and then test its functionality using three
empty methods. With this, component classes can be tested immediately,
which should make development a lot less buggy.