Adding support for Mobile Browser

[gregavola]

This pull request allows for mobile browsers to be able to use the slider functionality. It will automatically detect if the browser supports touch events and then change the mouseover to touchstart.

[pbowyer]

While this adds touch support (and works well) it:

1. Breaks dragging the slider in IE8
2. Removes the 'highlight' behaviour, which colours the progress

Hope that helps someone else who tries this patch!

[mariobischof]

only works on mac devices to me, on android the slider has a choppy behaviour. I think is somehow gets in the way with touch-scrolling.