Revert hard require on epel for CentOS 7

This leaves some of the documentation about epel, and installs it for
acceptance tests, but leaves it up to users on CentOS to include this
separately if needed.

Fixes #995

README.md

@@ -49,7 +49,7 @@ These are now documented via [Puppet Strings](https://github.com/puppetlabs/pupp
 
 You can view example usage in [REFERENCE](REFERENCE.md).
 
-**[puppet/epel](https://forge.puppet.com/modules/puppet/epel) is a soft dependency. The module requires it if you're on CentOS 7**
+**[puppet/epel](https://forge.puppet.com/modules/puppet/epel) is a soft dependency. On CentOS, with `$repos_ensure` set to `false` (current default), it may be required.
 
 Version v13.2.0 and older also added an erlang repository on CentOS 7. That isn't used and can be safely removed.
 

manifests/init.pp

@@ -507,8 +507,6 @@
       default: {
       }
     }
-  } elsif ($facts['os']['family'] == 'RedHat' and $facts['os']['release']['major'] == '7') {
-    require epel
   }
 
   contain rabbitmq::install

spec/acceptance/class_spec.rb

@@ -15,7 +15,12 @@
   context 'default class inclusion' do
     let(:pp) do
       <<-EOS
-      include rabbitmq
+        # Hack to make sure tests work w/ soft EPEL dependency on CentOS / EL7
+        if ($facts['os']['family'] == 'RedHat' and $facts['os']['release']['major'] == '7') {
+          require epel
+        }
+        include rabbitmq
+        Class['epel'] -> Class['rabbitmq']
       EOS
     end