Improve notification contents

Include sensible descriptions of non-content messages. For group
messages, display the sender's name and avatar rather than the group's.

js/models/messages.js

@@ -43,6 +43,16 @@
         isIncoming: function() {
             return this.get('type') === 'incoming';
         },
+        getDescription: function() {
+            if (this.isGroupUpdate()) {
+                return 'Updated the group';
+            }
+            if (this.isEndSession()) {
+                return 'Secure session ended';
+            }
+
+            return this.get('body');
+        },
         getContact: function() {
             if (this.collection) {
                 return this.collection.conversation.contactCollection.get(this.get('source'));

js/panel_controller.js

@@ -50,15 +50,18 @@
     window.notifyConversation = function(message) {
         if (Whisper.Notifications.isEnabled()) {
             var conversation = getConversation({id: message.get('conversationId')});
+            var sender = getConversation({id: message.get('source')});
             conversation.fetch().then(function() {
-                var notification = new Notification(conversation.getTitle(), {
+                sender.fetch().then(function() {
-                    body: message.get('body'),
+                    var notification = new Notification(sender.getTitle(), {
-                    icon: conversation.getAvatarUrl(),
+                        body: message.getDescription(),
-                    tag: conversation.id
+                        icon: sender.getAvatarUrl(),
+                        tag: conversation.id
+                    });
+                    notification.onclick = function() {
+                        openConversation(conversation.id);
+                    };
                 });
-                notification.onclick = function() {
-                    openConversation(conversation.id);
-                };
             });
             conversation.fetchMessages();
         } else {