Unicorn::Launcher

We don’t do a lot of standard daemonization stuff:

* umask is whatever was set by the parent process at startup
  and can be set in config.ru and config_file, so making it
  0000 and potentially exposing sensitive log data can be bad
  policy.
* don't bother to chdir("/") here since unicorn is designed to
  run inside APP_ROOT.  Unicorn will also re-chdir() to
  the directory it was started in when being re-executed
  to pickup code changes if the original deployment directory
  is a symlink or otherwise got replaced.