Sometimes callback executing before scrolling has finished

[joxerTMD]

Hello! I've found a little bug with callback mechanism.
In my app i'm relying on window.addEventListener('scroll', /** my super code **/ ).
I also relying on jumper's callback option, and sometimes callback executes before the last scroll event happens.
See: https://jsfiddle.net/mxqfjLge/ (I hope it will reproduce on your screen resolution)

i have prepared PR #56 to fix this

[joxerTMD]

Sry, is anybody here? This bug is significant to me. I'm of cause already using my own patched version of the library, but it would be great to use the offical one. If my solution makes no sense or incorrect it would be nice to know any other workaround :)