refactor main-app process

clean unnecessary codes

lib/main-window.js

@@ -2,6 +2,7 @@ const electron = require('electron')
 const app = electron.app
 const BrowserWindow = electron.BrowserWindow
 const path = require('path')
+const ipc = require('./ipc')
 
 var mainWindow = new BrowserWindow({
   width: 1080,
@@ -46,4 +47,8 @@ app.on('activate', function () {
   mainWindow.show()
 })
 
+app.on('before-quit', function (e) {
+  mainWindow.removeAllListeners()
+})
+
 module.exports = mainWindow