improve the dialog of software update

[kato1628]

New dialog image:

1. Careate update dialog for new app version
   • Not electron dialog.showMessageBox module but html content in BrowserWindow.
2. Show the following infomation about new app version in the dialog.
   • Realse notes (get contents from github release via github api)
   • Add button Remnind Me Later, Update Now, Skip This Version
3. Show download progress bar if the user click the button of Update Now
   • A example that use download-progress event of autoUpdater: https://github.com/iffy/electron-updater-example/blob/master/main.js
4. Show update dialog at the regular time
   • If the user click Remind Me Later button, show update dialog again 3 days later.
   • If the user click Skip This Version, the dialog is not shown until next version is released.

[kato1628]

In v0.5.0 the new dialog for notification of updates has added 🎉