Reset preview scroll position when post item is clicked

When scrolling through the preview of a long article, if the post was changed the scroll position of the preview would remain the same.

![ghostpreview](https://cloud.githubusercontent.com/assets/846587/3964791/7eb248d2-278d-11e4-80ce-6da126080df5.gif)

Ah wrong end of the stick, thanks for clarifying :)

That's a good shout, I've moved it in 506e44a. My worry with this method is does ember attach to every element or use event delegation?