slider over-running range.

[philip-keep]

Hi, nice project. I'd like to use it but I don't think that I'll be able to due to the following issue.
I was wanting to use it in a full screen overlay used for mobile and tablets. It works but the handle over-runs the width of the the screen. This happens on a physical mobile and using dev tools. the element should be 100% of the container width which has a little padding on either side. This happens in chrome and FF. For instance, if the screen is 505px, looking at the element inspector shows that it goes up to 498.971px

However, this is off the screen, due to the padding on the container. I hope that the feedback was off some use.