Provision Let's Encrypt certificate(s) for LV website #288

https://libvisual.org currently serves up GitHub's wildcard certificate (*.github.com) and will throw up invalid certificate errors in browser. GitHub can automatically provision Let's Encrypt certificates for custom domains like ours.

To do that, we first need DNS CAA records to be set. The records are a way to signal that Let's Encrypt is authorised to issue certificates for it.

The CAA record should look like one of the following:

Fully qualified:

libvisual.org.       CAA    0   issue "letsencrypt.org"

Partially qualified (relative to libvisual.org.):

@     CAA   0   issue "letsencrypt.org"

Either one is okay, depending on the DNS registrar's provided interface or zone configuration.

@dsmit, are you the owner of the libvisual.org domain? If you are, could you help us set this? Thanks in advance!