Removed scrollbars from cover images

Closes #704 

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Before
![image](https://cloud.githubusercontent.com/assets/302258/3913252/d5784724-2333-11e4-9c9c-c559a2a398a1.png)
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After
![image](https://cloud.githubusercontent.com/assets/302258/3913268/f0df0dae-2333-11e4-91ac-a0c825ae912e.png)