(fix) Check topic.constructor to reverse regression introduced by instanceof check

Author: indexzero

lib/vows/suite.js

@@ -142,7 +142,7 @@ 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 instanceof events.EventEmitter)) {
+            if (! (topic && topic.constructor === events.EventEmitter)) {
                 ctx.emitter = new(events.EventEmitter);
 
                 if (! ctx._callback) {