In this branch we're using Postgres triggers and stored procedures to send
notifications whenever a row is added to the `people` table and we're using
`Postgrex.Notifications` to subscribe to them. A substantian portion of the
code for this example comes from [this hackernoon post](https://hackernoon.com/get-notified-of-user-signups-and-plan-changes-automatically-using-postgres-phoenix-pubsub-e67d061b04bc).