Usage: php add_org.php <name> <slug> [nudge_email]

Examples:
  php add_org.php "Acme Corp" acme
    → Employees invite: nudge+acme@leapos.john-byrne.info

  php add_org.php "Acme Corp" acme nudge-acme@leapos.john-byrne.info
    → Employees invite: nudge-acme@leapos.john-byrne.info
    → Plus addressing also works as fallback