Five employees of Boston-based Springpad will join Google's Boston office as the online personal organizer app shuts its doors next month. Springpad, founded in 2008, told its users in a blog post last week it would be shutting its service down on June 25. Five engineers at Springpad, which had employed about 20 people full-time, will join Google's Boston office to work on Google Play Newsstand, an app that launched late last year, said Jeff Janer, co-founder of Springpad. Springpad couldn't generate…