Never append to a RELEASES file
Update.exe isn't SquirrelAware anymore, use the test assembly
Clean up the disaster that is post-install

Not only were we cleaning the app directory twice, we were also kicking out
our own executable out from under us (I *believe* with the idea, that it would
only apply on next reboot, which doesn't really work because those files get
turned into zombie files that are unreadable).
Clean up the package directory on cleanup