Paddle class has had a slight amendment to the code. Added a slideUp 
and slideDown method to make the code more readable and to not have 
random numbers (using getters and setters) in the KeyboardInput class.

Ball class has had 3 new methods implemented: isOutOfBounds, 
changeDirection and moving. They all do/will what their name implies.

Have also created enums for the Ball class as UP, DOWN, LEFT & RIGHT
will be constant values.

Also removed useless setters from multiple classes.

Screen is now implementing logic into the game.