Adding Behavior for Slider.js.

You might also put off the finding of these targets until change-time. This would allow you to ajax in new content that included the target. We don't always do this everywhere, and there's the possibility of these (relatively expensive) searches affecting performance if it's attached to the slider. Maybe you update it on complete? Just a thought. It's one of those gotchas that can bite you 6 months later when you can't figure out why your form doesn't work twice...