Add documentation stub for Ember.Router

Adding /** @scope Ember.Router.prototype */ makes YUIdoc print out the
entire router definition, without any error message. It doesn't actually
blow up, it just prints source. It's strange.

The method listing don't seem right yet -- it contains methods like
Ember.Route#controllerFor. But it's a start.
Merge pull request #1858 from CrowdStrike/router-doc

Add documentation stub for Ember.Router