Ultrahook for testing email to app

When testing ActionMailbox and Postmark, for example when testing our reply-by-email feature on ZipMessage, you must run Ultrahook in terminal.

Run the following when testing email to app on ZipMessage. Bastin (from Mallow Tech) had set this up by following Postmark's docs here.

echo "api_key: 9wxh5VaJxMrC08KaFUEq3bvGMfudAwlS" > ~/.ultrahook

ultrahook inbound-demo 3000