Add media service to image rewriting

Waiting on a NGINX config change for this to go through.
Images from the media service need to be rewritten with `/media` prefixed as discussed with @phamann.

![Cameras](http://gifshost.com/012012/1327341659_lightning_caught_on_camera.gif)
Would it be cleaner to route to `/media` or `/static`, rather than the more ambiguous `/media` / `/`? I realise the former would require a tad bit more coordination to release, but might end up in a better place.