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)

I think for the moment it's ok. I don't think the user will necessarily care too much about the message at that stage, it's still somewhat contextual. I'm also hoping to move all layers to prerendering soon so that the need for `!!this.prerender.template` isn't needed