title: Getting error using 'belongs_to' in Ecto phoenix.gen.html
body: <p>I'm making an model that I want to create in relationship to my user model. Following from <a href="http://www.phoenixframework.org/v0.13.1/docs/ecto-models#section-data-relationship-and-dependencies" rel="noreferrer">http://www.phoenixframework.org/v0.13.1/docs/ecto-models#section-data-relationship-and-dependencies</a> used the phoenix.gen.html as follows:</p>
  
  <pre><code>W:runcible&gt;mix phoenix.gen.html Ansible ansibles ansible_name:string ansible_description:text user:belongs_to
  </code></pre>
  
  <p>But I Get the following when i run it.  </p>
  
  <pre><code>Compiled web/models/user.ex
  Compiled web/controllers/user_controller.ex
  Generated runcible app
  ** (Mix) Unknown type `belongs_to` given to generator
  </code></pre>
  
  <p>Any ideas where I've made a mistake?</p>