Generate docs and link to 0.16

- Generate docs  (biggest change was moving validations to its own page, moving ErrorsSet & Validator to `App Internals` section)
- Add links to 0.16 and batman-master. It looks like this at the moment:
  
  ![image](https://cloud.githubusercontent.com/assets/2231765/2936712/efaf624c-d86c-11e3-849d-d5e7e63be438.png)

  Which is OK with me, but if you want to do some style magic, go for it :)

- __Sample Project__ still points to 0.15 -- should I just hide it? or try to update it? I've never looked at it is all...