Reorganised SOH to promote nodebots. Added code retreat summary page

How about keeping this consistent with the NodeSchool copy?

![image](https://cloud.githubusercontent.com/assets/51385/3568208/7de96cfa-0b2c-11e4-9f3a-04d42c1c2a61.png)

(so, move it down below the button, and have the copy as "Code Retreat has finished - see how it went")