Work with rootURL other than /

Hi, thanks for your great work on this project. It's really cool to see Ember being used to bootstrap something that I can hand off directly to non-developers and watch them get stuff done really quickly.

We want to deploy this internally on an existing subdomain with an alternate rootURL. I've changed rootURL in config/environment.js but it seems that ember-data is using absolute paths so the requests for versions.json and pages.json are failing.

Have there been any thoughts around this? I can work on a PR if it seems reasonable.