Add delay slider

This adds a "delay" attribute to the slider that prevents the model from updating until the user has stopped moving the slider for the specified amount of time. I adapted [this Stackoverflow answer](http://stackoverflow.com/a/3694388).

My use case is that I have a slider which causes things to be drawn on a Google map, and the slider changes were so quick that the drawing isn't able to keep up.

There is also a fix for the demo page. A fresh ```bower install``` places