range input improvement

fixes https://github.com/mapbox/mapbox-studio/issues/994

![oninput](https://cloud.githubusercontent.com/assets/865298/5051600/4e00257e-6bee-11e4-9f6e-968b1de183b5.gif)

I grepped the folder for all occurrences of rangeHandler, and replaced the onchange listeners with oninput listeners.

![screen shot 2014-11-14 at 10 52 57 am](https://cloud.githubusercontent.com/assets/865298/5051603/519d3f78-6bee-11e4-9498-23c8aeeee912.png)