Increase coverage metrics

Before:
![screen shot 2014-09-15 at 00 37 06](https://cloud.githubusercontent.com/assets/144476/4265944/1489945c-3c68-11e4-92d8-0274df9c453f.png)

After:
![screen shot 2014-09-15 at 00 36 23](https://cloud.githubusercontent.com/assets/144476/4265945/152820e0-3c68-11e4-918c-f0654d376559.png)

Is this correct behaviour for getImageRecipe? The code looks weird.

https://github.com/iplayer/bamboo/blob/develop/src/Bamboo/Models/Elements.php#L142