Fixed positioning of blockers on post editor

During changing posts in Arlima list form on the right gets reloaded to present currently selected post.
When new post has image with different dimensions that previously selected - blockers (marked in red) are positioned improperly, what can be seen on gif below:

![blockers](https://cloud.githubusercontent.com/assets/2885298/4556454/3ae74450-4ec9-11e4-9927-d72f9e22668f.gif)

That is happening because blocker divs are positioned before image gets loaded.

This fix is binding blockers positioning function to image loaded event so they get positioned after image takes it's place.