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)

Might be more transparent to simply make the element an argument rather than context.

i.e.

```js
toggleChildren(this, false, 0);

// ...

function toggleChildren(element, value, duration) {
  var toggle = $(element);
 // ...
}