Player Moves updated

-Add comments to describe the different movements
-player1Position.Y is changed from 1 to 10 to make the movements
noticeable
-player1Position.Y if being checked to make sure it is not going off the
screen
-player2Position.Y movements are added with up and down keys
-player2Position.Y are checked to make sure not going off screen
-player2Position are set and game screen is refreshed