Fixes chrome scroll bug in fixed elements

-webkit-transform: translateZ(0);  Seemed to solve the weird bug:
![screen recording 2014-10-22 at 01 33 pm](https://cloud.githubusercontent.com/assets/566971/4739524/5e0eedb0-5a05-11e4-8d1c-12800a8ed3b6.gif)

Closes #845