Made a change that eliminates the following bug (see http://github.co…

…m/cloudhead/vows/issues#issue/16): Sometimes you want to test an object that inherits from EventEmitter. In this case, if you return said testable object as the topic, then the code hangs if the EventEmitter subclass instance that I'm testing doesn't emit "success" or "error."

lib/vows/suite.js

@@ -140,7 +140,7 @@ 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) {