Resolves #239; URL & page state consistency

I agree with issue opener @quangv that the back button should return to you to the same state that you came from. In this case it makes sense that this URL should always return you to the index when you consider the comparable behaviour in changing a URL by addition.

I believe @tomdale is pro stateful URLs e.g. [this post on his blog](http://tomdale.net/2012/05/ember-routing/).