title: Sonata Formatter Bundle generates an empty textarea
body: <p>I want to use Ckeditor or markdown text editor in my admin panel of project</p>
  
  <p>I have installed FormatterBundle , Ivory\CkeditorBundle, and Knp\MarkdownBundle in my project ....</p>
  
  <p>in my PostAdmin.php</p>
  
  <pre><code>namespace Main\Bundle\MainBundle\Admin;
  use Sonata\AdminBundle\Admin\Admin;
  use Sonata\AdminBundle\Datagrid\DatagridMapper;
  use Sonata\AdminBundle\Datagrid\ListMapper;
  use Sonata\AdminBundle\Show\ShowMapper;
  
  class PostsAdmin extends Admin
  
  /**
   * @param FormMapper $formMapper
   */
  protected function configureFormFields(FormMapper $formMapper)
  {
      $formMapper
          -&gt;add('id')
          -&gt;add('title')
          -&gt;add('shortDescription')
          -&gt;add('text', 'sonata_formatter_type', array(
              'source_field'         =&gt; 'text',
              'source_field_options' =&gt; array('attr' =&gt; array('class' =&gt; 'span10', 'rows' =&gt; 20)),
              'format_field'         =&gt; 'text',
              'target_field'         =&gt; 'text',
              'ckeditor_context'     =&gt; 'default',
              'event_dispatcher'     =&gt; $formMapper-&gt;getFormBuilder()-&gt;getEventDispatcher()
          ))
          -&gt;add('created')
          -&gt;add('updated')
          -&gt;with('Gallery')
              -&gt;add('gallery', 'sonata_type_model_list', array(
                      'cascade_validation' =&gt; true,
                  ), array(
                      'edit'              =&gt; 'inline',
                      'inline'            =&gt; 'table',
                      'sortable'          =&gt; 'position',
                      'link_parameters'   =&gt; array('context' =&gt; 'posts'),
                      'admin_code'        =&gt; 'sonata.media.admin.gallery'
                  )
              )
          -&gt;end()
      ;
  }
  </code></pre>
  
  <p>my config.php is ..</p>
  
  <pre><code>sonata_formatter:
      formatters:
          markdown:
              service: sonata.formatter.text.markdown
              extensions:
                  - sonata.formatter.twig.control_flow
                  - sonata.formatter.twig.gist
                  - sonata.media.formatter.twig #keep this commented unless you are using media bundle.
  
  
          text:
              service: sonata.formatter.text.text
              extensions:
                  - sonata.formatter.twig.control_flow
                  - sonata.formatter.twig.gist
                  - sonata.media.formatter.twig
  
  
          rawhtml:
              service: sonata.formatter.text.raw
              extensions:
                  - sonata.formatter.twig.control_flow
                  - sonata.formatter.twig.gist
                  - sonata.media.formatter.twig
  
  
          richhtml:
              service: sonata.formatter.text.raw
              extensions:
                  - sonata.formatter.twig.control_flow
                  - sonata.formatter.twig.gist
                  - sonata.media.formatter.twig
  
  
          twig:
              service: sonata.formatter.text.twigengine
              extensions: [] # Twig formatter cannot have extensions
  
      ckeditor:
              templates:
                  browser: 'SonataFormatterBundle:Ckeditor:browser.html.twig'
                  upload: 'SonataFormatterBundle:Ckeditor:upload.html.twig'
  
  
  ivory_ck_editor:
      default_config: default
      configs:
          default:
              filebrowserBrowseRoute: admin_sonata_media_media_ckeditor_browser
              filebrowserImageBrowseRoute: admin_sonata_media_media_ckeditor_browser
              # Display images by default when clicking the image dialog browse button
              filebrowserImageBrowseRouteParameters:
                  provider: sonata.media.provider.image
              filebrowserUploadRoute: admin_sonata_media_media_ckeditor_upload
              filebrowserUploadRouteParameters:
                  provider: sonata.media.provider.file
              # Upload file as image when sending a file from the image dialog
              filebrowserImageUploadRoute: admin_sonata_media_media_ckeditor_upload
              filebrowserImageUploadRouteParameters:
                  provider: sonata.media.provider.image
                  context: posts # Optional, to upload in a custom context
  </code></pre>
  
  <p>Please give an advice why my textarea is an empty ??</p>