fix sliders on Kantorowski

- Kantorowski sliders needed to use new eventDetails property (newValue instead of value)
- Slider needed to handle being drawn into a container that already had a slider in it.

@lbondaryk So it turns out that the Kantorowski page is drawing both sliders into the same span as a container (it wasn't supposed to it's a typo which I didn't fix). That turned out to be a good test, catching a bug I had created in the slider.