Fix CustomEvent for older IE

custom-event.js

  (function () {  // bootstrap CustomEvent for IE
    if (typeof window.CustomEvent === 'function') return false;

    function CustomEvent (event, params) {
      params = params || {bubbles: false, cancelable: false, detail: undefined};
      var evt = document.createEvent('CustomEvent');
      evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail);
      return evt;
    }

    CustomEvent.prototype = window.Event.prototype;

    window.CustomEvent = CustomEvent;
  })();