Added lots of 'final' modifiers to class fields where applicable.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>

src/itdelatrisu/opsu/states/SongMenu.java

@@ -209,7 +209,7 @@ public class SongMenu extends BasicGameState {
 	private GameContainer container;
 	private StateBasedGame game;
 	private Input input;
-	private int state;
+	private final int state;
 
 	public SongMenu(int state) {
 		this.state = state;