Unpermitted Parameters when working with EmberJS

I'm trying to learn how to use emberjs as a client of a rails api!

My code lives here: http://ift.tt/21nJf1w

Is a simple rails-api that provides CRUD operations by the restful endpoints. I'm following this tutorial but when I try to save a comment in blog post, I receive a Unpermitted params: :post.

How can I solve this problem?