Merge branch 'yahtzee'

src/main/java/io/zipcoder/casino/Yahtzee.java

@@ -176,7 +176,7 @@ public class Yahtzee extends DiceGame implements Game, Gamble{
 
     @Override
     public void bet(int betAmount) {
-        dicePlayer.getPlayer().changeBalance(betAmount);
+        dicePlayer.getPlayer().changeBalance(betAmount * -1);
     }
 
     @Override