[Fixes #305] Confuse webpack

Cc @TheLarkInn, is there a better way?

Author: stefanpenner

lib/es6-promise/asap.js

@@ -96,8 +96,7 @@ function flush() {
 
 function attemptVertx() {
   try {
-    const r = require;
-    const vertx = r('vertx');
+    const vertx = Function('return this')().require('vertx');
     vertxNext = vertx.runOnLoop || vertx.runOnContext;
     return useVertxTimer();
   } catch(e) {