Imgur integration inside image tests

Integrates links to failed image tests directly in exception message.

![screenshot from 2014-06-17 20 41 45](https://cloud.githubusercontent.com/assets/1842780/3304861/9d82a172-f64f-11e3-8814-919693a9337c.png)

![screenshot from 2014-06-17 20 41 56](https://cloud.githubusercontent.com/assets/1842780/3304865/a3aa8ea2-f64f-11e3-8633-ff5fed82cccb.png)