+ Added 2 new enemies (Goats and Snakes)
+ Created a super class called Enemy.
+ Moved most variables and methods from Chicken class to Enemy class
+ Renamed most of the chicken variables and methods to 'enemy' in Enemy
class
+ Chicken, Goat en Snake classes inherited from Enemy class.
+ added new images for Goat and Snake in 'GameFiles' folder.
+ added new WAV sounds for Goat and Snake in GameFiles' folder.
+ added a BounceAroundScreen() method in Game class to keep enemies
within screen
+ Start Screen now starts in the center of the monitor
+ Game Screen also starts in the center of the monitor
+ Enemies (Chickens, Goats and snakes) now move to 'Random' locations on
the Game Screen as soon they pop up.