SSL certificates not updating

[YPCrumble]

I'm getting an intermittent error which is that my SSL certificates are failing to update. I'm pretty sure this is because of using unattended-upgrades which adds security patches to certbot, but we do not currently reboot the server when required. This is causing certbot to fail because the new binary can't run without the reboot.

My suggestion is to add the automatic reboot option when unattended-upgrades adds a security patch that requires a reboot to be in effect. Though this might cause downtime, it also ensures that the server is patched as soon as any security patch is released.

Related to #118

[DmytroLitvinov]

Also, I guess this repo will support Ubuntu 20.04 in the future and certbot-auto will be deprecated. As a recommendation, we should migrate to certbot