Suggest some example hierarchies

README.md

@@ -214,6 +214,25 @@ global ruby version, service ports, etc). This repository supplies a
 starting point for your Hiera configuration at `config/hiera.yml`, and an
 example data file at `hiera/common.yaml`. See those files for more details.
 
+The default `config/hiera.yml` is configured with a hierarchy that allows
+individuals to have their own hiera data file in
+`hiera/users/{github_login}.yaml` which augments and overrides
+site-wide values in `hiera/common.yaml`. This default is, as with most of the
+configuration in the example repo, a great starting point for many
+organisations, but is totally up to you. You might want to, for
+example, have a set of values that can't be overridden by adding a file to
+the top of the hierarchy, or to have values set on specific OS
+versions:
+
+```yaml
+# ...
+:hierarchy:
+  - "global-overrides.yaml"
+  - "users/%{::github_login}"
+  - "osx-%{::macosx_productversion_major}"
+  - common
+```
+
 ### Node definitions
 
 Puppet has the concept of a