READY - Pairings with email notifications triggered by cron

This is ready to go.
* Will make recommendations among players that have emails in the system.
* You can opt out of recommendation by removing your email.
* There is currently no punishment for not playing recommended match.
* Requires `nconf.get('NODE_ENV')` to return `'prod'`.
* Should send emails at 7:30 on Monday.

If there are no objections, I'll merge and push this at 4:30, so we can see some recommendations at the start of next week.