Notes
-----

- The certificate key file must be readable by the "plugins" group, as Nginx is
  run by the "www-adm" user and "www-adm" is in the "plugins" group.

- The file nagios-plugins.crt includes our certificate, followed by the StartSSL
  intermediate¹ certificate, followed by the root² certificate.

¹ https://www.startssl.com/certs/sub.class1.server.ca.pem
² https://www.startssl.com/certs/ca.pem