Improve button and keystrokes handling

src/main/java/wtf/beatrice/autosqueal/util/RunnerUtil.java

@@ -4,6 +4,10 @@ import java.awt.*;
 
 public class RunnerUtil {
 
+    private RunnerUtil() {
+        throw new AssertionError("The RunnerUtil class is not intended to be instantiated.");
+    }
+
     public static final int SECONDS_BETWEEN_MOVES = 10;
 
     public static final int SCREEN_HEIGHT = Toolkit.getDefaultToolkit().getScreenSize().height;