debugging

* included example from http://carlsednaoui.github.io/ouibounce/
* seems that clientY is handled differently between `mousemove` and
`mouseleave` events, maybe screenY is better?
http://stackoverflow.com/questions/6073505/what-is-the-difference-between-screenx-y-clientx-y-and-pagex-y
fixed Y-coordinate disparity

* seems that getting the Y coord from screenY differs in `mousemove` vs
`mouseleave`
* switch from clientY to screenY necessitates changing sensitivity
accordingly, since screenY includes browser chrome