Layers transition correctly

This time it handles scrolling. No need for scroll top.


![layers-with-scroll](https://cloud.githubusercontent.com/assets/814861/5318024/588c795a-7c94-11e4-955d-e726e5096061.gif)

This is just a not very well named attribute which means, decorate the preloader with a white background shape with a box shadow on it.

That's not as catchy though. 

Leaving it for now, but can revisit if required in a separate PR.