Update display test case

example/advanced/Power_Measurements/Display/Display.ino

@@ -23,4 +23,10 @@ void loop() {
     dezibot.display.println(iter);
   }
   delay(10);
+  //Completely off
+  dezibot.display.clear()
+  sleep(10);
+  //Completely on
+  dezibot.display.invertColor();
+  sleep(10);
 }