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)

also remy it isn't more flexible, that's not true at all. it's just not.
and this way the styles stay entirely the business of the stylesheets and not of the haml's configuration arguments.

this is way is just as flexible. i don't even understand in the slightest what you mean by "that makes it way more flexible"
in what was does it make it more flexible? wtf