Expand menu buttons when hovering.

Added hovering capabilities to GUIMenuButton.  The max scale and direction to expand the image can be modified per object.

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

src/itdelatrisu/opsu/Utils.java

@@ -197,6 +197,7 @@ public class Utils {
 		backButton = new GUIMenuButton(back,
 				back.getWidth() / 2f,
 				height - (back.getHeight() / 2f));
+		backButton.setHoverDir(GUIMenuButton.Expand.UP_RIGHT);
 
 		// set default game images
 		for (GameImage img : GameImage.values())