**Make amp example valid**
I'm using amp validator chrome plugin which shows that `meta charset=utf-8` is duplicated.
I assume that `Head` component adds `<meta charset="utf-8" class="next-head next-head">`
anyway.
And this line just duplicating it.
<img width="987" alt="screen shot 2018-06-06 at 15 54 45" src="https://user-images.githubusercontent.com/1488195/41036743-198ca00a-69a2-11e8-978c-5a5cb5a994d2.png">
* Added Google AMP example
* Added styles and a second page
* Using regular anchor since there is no client-side routing
* Added comment on react config for amp