Set conversation type when creating from sync message

When a conversation is created as the result of a sync message, and it
is not a group, we need to set its type to private.

// FREEBIE

js/models/messages.js

@@ -140,7 +140,7 @@
                 var conversation = new Whisper.Conversation({id: conversationId});
                 conversation.fetch().always(function() {
                     var now = new Date().getTime();
-                    var attributes = {};
+                    var attributes = { type: 'private' };
                     if (pushMessageContent.group) {
                         var group_update = {};
                         attributes = {