Expandible sitemap

Adds support for expanding and collapsing children in the sitemap. State is saved in localStorage for convenience.

![screen shot 2014-09-24 at 16 00 13](https://cloud.githubusercontent.com/assets/770763/4390230/8ebb4c94-43fb-11e4-92d9-ba1ab44873af.png)

Subscript operator works across the board right?

```js
localStorage['sitemap.hidden'] = JSON.stringify(ids)
```