Issue when placed within an absolutely positioned element

[chrisbell08]

When the slider is within an absolutely positioned element it doesn't set the start value of the slider. I've created an example on codepen: http://codepen.io/anon/pen/yMPEpb

On my code the slider still works but just just doesn't start in the correct place but the codepen it doesn't work at all, not sure if that's just down the codepen using an older version (I forked your demo pen)