title: ActiveAdmin ForbiddenAttributesError
body: <p>i am a brand new for Ruby on Rails.
  I am using a ActiveAdmin and i have a problem with creating a AdminUser</p>
  
  <p><strong>ActiveModel::ForbiddenAttributesError in Admin::AdminUsersController#create
  ActiveModel::ForbiddenAttributesError</strong></p>
  
  <p><strong><em>Request</em></strong></p>
  
  <p><strong>Parameters:</strong></p>
  
  <ul>
  <li><p>{"utf8"=>"✓",</p></li>
  <li><p>"authenticity_token"=>"nvV++6GNTdA/nDzw1iJ6Ii84pZPcv2mzg0PK2Cg9Ag0=",</p></li>
  <li><p>"admin_user"=>{"email"=>"admin2@example.com"},</p></li>
  <li><p>"commit"=>"Create Admin user"}*</p></li>
  </ul>
  
  <hr>
  
  <p><strong>Rails 4.1.0</strong></p>
  
  <p><strong>activeadmin 1.0.0</strong> </p>
  
  <p><strong>ruby 2.1</strong></p>
  
  <hr>
  
  <p><strong>app/admin/admin_user.rb</strong></p>
  
  <pre><code>ActiveAdmin.register AdminUser do
      index do
        column :email
        column :current_sign_in_at
        column :last_sign_in_at
        column :sign_in_count
        default_actions
      end
  
      form do |f|
          f.inputs "Admin Details" do
              f.input :email
          end
          f.actions
      end
  end
  </code></pre>
  
  <p><strong>app/models/admin_user.rb</strong></p>
  
  <pre><code>class AdminUser &lt; ActiveRecord::Base
      # Include default devise modules. Others available are:
      # :confirmable, :lockable, :timeoutable and :omniauthable
      devise :database_authenticatable, 
             :recoverable, :rememberable, :trackable, :validatable
  
      after_create { |admin| admin.send_reset_password_instructions }
  
      def password_required?
          new_record? ? false : super
      end
  end
  </code></pre>
  
  <p><strong>Gemfile</strong></p>
  
  <pre><code>source 'https://rubygems.org'
  
  gem 'rails', '4.1.0'                                                
  gem 'sqlite3'                                                       
  gem 'sass-rails', '~&gt; 4.0.3'                                        
  gem 'uglifier', '&gt;= 1.3.0'                                          
  gem 'coffee-rails', '~&gt; 4.0.0'                                      
  gem 'jquery-rails'                                                  
  gem 'turbolinks'                                                    
  gem 'jbuilder', '~&gt; 2.0'                                            
  gem 'activeadmin',      github: 'gregbell/active_admin' 
  gem 'polyamorous',      github: 'activerecord-hackery/polyamorous'
  gem 'ransack',          github: 'activerecord-hackery/ransack'      
  gem 'formtastic',       github: 'justinfrench/formtastic'           
  gem 'devise'
  
  gem 'sdoc', '~&gt; 0.4.0', group: :doc 
  </code></pre>
  
  <p><strong>config/environments/development.rb</strong></p>
  
  <pre><code>Rails.application.configure do
    # Settings specified here will take precedence over those in config/application.rb.
  
    # In the development environment your application's code is reloaded on
    # every request. This slows down response time but is perfect for development
    # since you don't have to restart the web server when you make code changes.
    config.cache_classes = false
  
    # Do not eager load code on boot.
    config.eager_load = false
  
    # Show full error reports and disable caching.
    config.consider_all_requests_local       = true
    config.action_controller.perform_caching = false
  
    # Don't care if the mailer can't send.
    config.action_mailer.raise_delivery_errors = false
  
    # Print deprecation notices to the Rails logger.
    config.active_support.deprecation = :log
  
    # Raise an error on page load if there are pending migrations.
    config.active_record.migration_error = :page_load
  
    # Debug mode disables concatenation and preprocessing of assets.
    # This option may cause significant delays in view rendering with a large
    # number of complex assets.
    config.assets.debug = true
  
    # Adds additional error checking when serving assets at runtime.
    # Checks for improperly declared sprockets dependencies.
    # Raises helpful error messages.
    config.assets.raise_runtime_errors = true
  
    # Raises error for missing translations
    # config.action_view.raise_on_missing_translations = true
  
    # Sending emails works
    config.action_mailer.default_url_options = { :host =&gt; 'localhost:3000' }
  end
  </code></pre>