title: How to use enum(rails 4.1)?
body: <p>I'm trying to use enum in my project.
  but I don't know how to use it with simple_form input collection.
  my code makes an error.
  this is my enum definition in user.rb:</p>
  
  <pre><code>    enum role: [ :guest, :super_admin, :advertiser, :publisher, :account_manager]
  </code></pre>
  
  <p>and this is my view code:</p>
  
  <pre><code>&lt;%= simple_form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %&gt;
      &lt;%= render 'devise/shared/error_messages', object: f.object %&gt;
      &lt;div class="form-inputs"&gt;
         &lt;%= f.input :name, required: true, autofocus: true%&gt;
         &lt;%= f.input :email, required: true %&gt;
        &lt;%= f.input :password, required: true, placeholder: "min. 6 characters",
                    input_html: {"parsley-minlength" =&gt; 6, "error-container" =&gt;"#errorBlock"} %&gt;
        &lt;%= f.input :password_confirmation, required: true,
                    input_html: {"parsley-equalto" =&gt; "#user_password"} %&gt;
        **&lt;%= f.input :role, collection: User.roles %&gt;**
  
      &lt;/div&gt;
  </code></pre>