I'm hosting this on Linode running Ubuntu and Nginx and I followed this tutorial at Digital Ocean which was damn simple to go through.
Letsencrypt is making things super easy to get SSL everywhere.
After finishing the setup (15m later) I found that the domain
jj.isgeek.net had the "Unsecure" icon on the URL bar. Turns out that some resources (the Stackoverflow widget) were being fetched from HTTP, so I just edited those to use their HTTPS coutnerparts (thankfully available) and I got the green padlock :)
When first installing it I forgot to add both domains to the initial
certbot command. I had to use the
\--expand argument in the same command to add the extra domain.
Also, note #issuecomment-175963980">this bug about using underscore in subdomains. You won't be able to use Letsencrypt if your subdomain contains an underscore!