Add wrapper for pub cover and pubcontent divs.

#5855 

This PR addresses https://github.com/openscholar/openscholar/issues/5855#issuecomment-41519930

Output:
![selection_112](https://cloud.githubusercontent.com/assets/4497748/2813672/8f7cdd2e-ce93-11e3-978a-1cc334103572.png)