Fix site not loading on initial request

This should fix the issue where the site doesn't load on the initial request.

Forum thread: http://forums.hummingbird.me/t/first-time-entering-dashboard-doesnt-load/16533/5

This seems to be caused by the removal of the `cookie_auth` Warden strategy a few weeks back, due to this removal the `user_signed_in?` call was returning false and therefore not preloading the users data causing Ember to crash.

Also adds a fix for Ember Inspector breaking when inspecting the `user` or `user-info` models.