Update ion.rangeSlider.js for multiple ranges bug

Hello,
i use your awesome plugin in a website and i found a bug. I search a little and find a fix.

The bug is : when you have two or more ranges side by side, if you start by draggin on range 1 and release on range 2, it affects the change on range 2. It seems a little weird (you can see it on you demo website)

I fix that by testing which instance i am using and also by incrementing a variable to allow the move to click function.