Navigator pushState at getting started

- Move `tutorial-navigator` to **Getting started** page.
- Add `pushState` and hashed routes for `tutorial-navigator`.
- Remove from sidebar all tutorials included in `tutorial-navigator`.
- Update getting started texts.


![image](https://cloud.githubusercontent.com/assets/367429/3221276/b105dcec-f009-11e3-8250-c9689ff8230d.png)