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)

I do understand what you mean for Native for example, but for SPAs and Regular web apps it's not the same.

Also, we could change the name to be `native-mobile/android-cell/...`.

The idea is not only that this is user friendly, but also that it's better for SEO. A lot of people google for FrontEnd maybe and not SPA. Or backend instead of just `regular-webapp`. This way, with more words, Google will rank us better for those cases which is exactly what we want with documentation. That's even more important than a nice URL IMHO.