message: Add createThread method
diff: @@ -93,6 +93,11 @@ export default Service.extend({
  message.handle();
  },
  + createThread(...messages) {
  + let thread = this.get('store').createRecord('thread', { messages });
  + return thread.save();
  + },
  +
  createMessage(properties={}) {
  let messageProperties = assign({
  sentAt: moment(),
  