use instanceof to check if the return value from a topic is an EventEmitter

Signed-off-by: seebees <seebees@gmail.com>

Author: seebees

lib/vows/suite.js

@@ -144,7 +144,7 @@ this.Suite.prototype = new(function () {
 
             // If the topic doesn't return an event emitter (such as a promise),
             // we create it ourselves, and emit the value on the next tick.
-            if (! (topic && topic.constructor === events.EventEmitter)) {
+            if (! (topic instanceof events.EventEmitter)) {
                 ctx.emitter = new(events.EventEmitter);
 
                 if (! ctx._callback) {