More stack navigation flow

  Instead of continually adding to the end this illustrates adding
  a view controller next to the current view controller.

ExampleStoryboard/PSStackedStoryboardExample/PSViewController.m

@@ -42,7 +42,7 @@ - (void)pushViewControllerWithColor:(UIColor *)color {
     [[viewController view] setBackgroundColor:color];
     [viewController setShowBackButton:YES];
 
-    [[self stackController] pushViewController:viewController animated:YES];
+    [[self stackController] pushViewController:viewController fromViewController:self animated:YES];
 }