Added AutoLocation 'auto' option for automatic location setting based off support

Some people would like to support the history API but auto fallback to hashchanges in older browsers. The current way they could do that is check for support themselves and dynamically set the location property when they reopen the Router, but this makes it easy for them to not need that boilerplate code.

With the AutoLocation class, users can now just use:

```javascript
App.Router.reopen({
  location: 'auto'
});
```