title: Why am I getting "Unpermitted parameter: format"?
body: <p>I'm getting these parameters in my Rails controller:</p>
  
  <pre><code>Parameters: {"id"=&gt;"238", "user_id"=&gt;1, "group_id"=&gt;43, "title"=&gt;"asdasdasd 1111 ultadas ult asdas", "description"=&gt;"asdssss", "state_id"=&gt;nil, "allow_anonymous_answer"=&gt;false, "initial_message"=&gt;"asdasdsadas", "final_message"=&gt;"dasdasdsad", "poll_pages"=&gt;[{"id"=&gt;382, "poll_id"=&gt;238, "title"=&gt;"Pagina 1", "description"=&gt;"Pagina 1", "position"=&gt;1, "created_at"=&gt;"2016-05-06T14:25:56.795Z", "updated_at"=&gt;"2016-05-06T14:25:56.795Z"}], "poll"=&gt;{"id"=&gt;"238", "user_id"=&gt;1, "group_id"=&gt;43, "title"=&gt;"asdasdasd 1111 ultadas ult asdas", "description"=&gt;"asdssss", "state_id"=&gt;nil, "allow_anonymous_answer"=&gt;false, "initial_message"=&gt;"asdasdsadas", "final_message"=&gt;"dasdasdsad"}}
  </code></pre>
  
  <p>Yet I get this message: <code>Unpermitted parameter: format</code></p>
  
  <p>Even though I'm using:</p>
  
  <pre><code>params.permit(:id, :user_id, :title, :description, :state_id, :group_id, :allow_anonymous_answer, :initial_message, :final_message, poll: [:id, :user_id, :title, :description, :state_id, :group_id, :allow_anonymous_answer, :initial_message, :final_message], poll_pages: [:id, :poll_id, :title, :description, :position, :created_at, :updated_at])
  </code></pre>