Dynamic contributor images

Things to note.

**1** We now have three static hosts - a44eade

```
assets.path=http://aws-frontend-static.s3.amazonaws....
images.path=http://frontend-ImageLoa-116VI2UPNRZI....
static.path=http://static.guim.co.uk
```

- assets = our javascript, css etc.
- images = the dynamic/responsive image server 
- static = the static image server 

**2** There's a switch that toggles between the dynamic and static hosts - dd9d127

At the moment this is just designed to test the 140x140px profile page photo's.