trigger the event in the order of the event context. Same semantics as `Sammy.EventContext#trigger()`. If data is ommitted, `content` is sent as `{content: content}`
function(name, data) {
      return this.then(function(content) {
        if (typeof data == 'undefined') { data = {content: content}; }
        this.event_context.trigger(name, data);
      });
    }