Update NoticesController to use ES6 destructuring, const, let

app/scripts/notice-controller.js

@@ -1,4 +1,4 @@
-const EventEmitter = require('events').EventEmitter
+const {EventEmitter} = require('events')
 const semver = require('semver')
 const extend = require('xtend')
 const ObservableStore = require('obs-store')
@@ -46,8 +46,8 @@ module.exports = class NoticeController extends EventEmitter {
   markNoticeRead (noticeToMark, cb) {
     cb = cb || function (err) { if (err) throw err }
     try {
-      var notices = this.getNoticesList()
-      var index = notices.findIndex((currentNotice) => currentNotice.id === noticeToMark.id)
+      const notices = this.getNoticesList()
+      const index = notices.findIndex((currentNotice) => currentNotice.id === noticeToMark.id)
       notices[index].read = true
       notices[index].body = ''
       this.setNoticesList(notices)