Stop using the polyfill when you are assign the es6-promise after tha…

…t anyway

es6-promise.polyfill() is broken for Chrome atm and replaces the native Promise and swallows unhandled errors.
stefanpenner/es6-promise#70

JitsiMeetJS.js

@@ -121,7 +121,6 @@ var LibJitsiMeet = {
     }
 };
 
-require("es6-promise").polyfill()
 //Setups the promise object.
 window.Promise = window.Promise || require("es6-promise").Promise;