Ensure EPEL is configured before installing plugin
Ensure EPEL is configured before installing plugin

I've noticed other PRs fail because puppet is trying to install the
dns_rfc2136 package before EPEL has been configured. The cleanest way of
fixing this seems to be to have the plugin class `require letsencrypt`.
There are only two resources in the `letsencrypt::plugin::dns_rfc2136`
and the `file` resource already required `Class['letsencrypt']`. Now the
`package` resource will too.

The base class already `contain`s `letsencrypt::install` and that
`include`s `epel` and configures the correct ordering.

danzilio/puppet-letsencrypt