Update _posts/2013-01-10-building-an-ember-app-with-rails-api-part-3.md

Removing the comment about asking for how to set the defaults in the model itself.  Missed that last time.
Merge pull request #23 from justinbkay/patch-10

Update _posts/2013-01-10-building-an-ember-app-with-rails-api-part-3.md