Fix header image

Images from `content/images/` gets copied out by default to
`/images`.
Those making chapos have probably been seeing this ...
![no_profile](https://f.cloud.github.com/assets/3141711/1276396/2553ee26-2e64-11e3-94aa-dee7772c82dc.png)

You should now have a nice round header image like so ...
![working_profile](https://f.cloud.github.com/assets/3141711/1276397/60ab5fea-2e64-11e3-9749-b804369ad28e.png)