Prevent witness embeds from being picture cleaned

We recently changed the way we manage/style inline images below 400px, this was affecting witness embeds with low quality user generated uploads. This simply prevents witness embeds from being picture cleaned.

#### Before
![google chrome](https://f.cloud.github.com/assets/80089/1277667/9ff37724-2ed6-11e3-9987-826ac3f820a5.png)

#### After
![google chrome](https://f.cloud.github.com/assets/80089/1277668/a2e8c024-2ed6-11e3-9ad6-f262ba7fe29d.png)