fixed tinymce visual editor css

common/static/css/tiny-mce.css

 @import url(//fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,400,300,600,700);
 
-.mceContentBody {
+.mce-content-body {
     padding: 10px;
     background-color: #fff;
     font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;