Router now observes the 'title' property on route handlers and sets document.title

I needed a way to automate title setting for routes and figured others may too.

Router now observes the 'title' property on route handlers, combines them, and sets it as the document's title.

It appears https://github.com/emberjs/ember.js/issues/2262 requests this as well.

If the feature isn't used, the document title is not touched or overwritten.

e.g.

```javascript
App.ApplicationRoute = Ember.Route.extend({
    title: 'My Application'
});

App.AboutRoute = Ember.Route.extend({
    title: 'About'
});
```

If you viewed /about, the title would be set as "About - My Application". The order in which the route titles are appended was based off what I see others doing around the web, particularly in Gmail.

The title properties are observed, so you Gmail-like features of updating the title when a new email is here can easily be done. To change the divider that is used, just override the titleDivider property on the router.

Let me know your thoughts.