Fix up unsupported attachment rendering

Rather than simply displaying an inactionable error, render a link that
allows the user to save the unsupported attachment.

// FREEBIE

js/views/message_view.js

@@ -100,12 +100,13 @@
         },
         loadAttachments: function() {
             this.model.get('attachments').forEach(function(attachment) {
-                var view = new Whisper.AttachmentView({ model: attachment }).render();
+                var view = new Whisper.AttachmentView({ model: attachment });
                 this.listenTo(view, 'update', function() {
                     this.trigger('beforeChangeHeight');
                     this.$('.attachments').append(view.el);
                     this.trigger('afterChangeHeight');
                 });
+                view.render();
             }.bind(this));
         }
     });