next button visibility should be automatic

[mschipperheyn]

In most cases you will script your joyride. However, in some cases, for instance when you use joyride to show off an x number of new items that is dynamically generated, you don't really know if there's a "next" guide. You can parse out the next button on that last item, but it would be nice if joyride was smart enough to not show the next button when there is no next.