Fix removed 'app' module in Electron v1.0.0

Electron v1.0.0 was out and deprecated modules are removed.
I fixed requiring deprecated module.

electron/electron#5373

index.js

@@ -1,14 +1,15 @@
 'use strict';
 
-var app = require('app');
+var electron = require('electron');
+var app = electron.app;
 var jsonfile = require('jsonfile');
 var path = require('path');
 var mkdirp = require('mkdirp');
 var objectAssign = require('object-assign');
 var deepEqual = require('deep-equal');
 
 module.exports = function (options) {
-  var screen = require('screen');
+  var screen = electron.screen;
   var state;
   var winRef;
   var stateChangeTimer;