Add documentation for yum group and install options

Author: yorickps

README.md

@@ -264,13 +264,17 @@ rpm -q "$PACKAGE_NAME" --qf '%|EPOCH?{%{EPOCH}}:{0}|:%{NAME}-%{VERSION}-%{RELEAS
 
 ### Install or remove *yum* package group
 
+Install yum [package groups](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/sec-working_with_package_groups).  To list groups: `yum group list`. Then use that name in your puppet manifest. With support for install_options (e.g. enable repos if disabled by default).
+
 ```puppet
 yum::group { 'X Window System':
-  ensure  => present,
-  timeout => 600,
+  ensure          => present,
+  timeout         => 600,
+  install_options => ['--enablerepo=*'];
 }
 ```
 
+
 ### Install or remove packages via `yum install`
 
 This is a workaround for [PUP-3323](https://tickets.puppetlabs.com/browse/PUP-3323).  It enables the installation of packages from non-repo sources while still providing dependency resolution.  For example, say there is a package *foo* that requires the package *bar*.  *bar* is in a Yum repository and *foo* is stored on a stand-alone HTTP server.  Using the standard providers for the `Package` resource type, `rpm` and `yum`, the `rpm` provider would be required to install *foo*, because only it can install from a non-repo source, i.e., a URL.  However, since the `rpm` provider cannot do dependency resolution, it would fail on its own unless *bar* was already installed.  This workaround enables *foo* to be installed without having to define its dependencies in Puppet.