(maint) Update Puppetfile versions, update style

This commit updates the Puppetfile example module versions to list the
latest releases for the example modules as of 2019-07-10, and also
updates several files for style.

Standardizing on double-quotes in YAML due to:

1. Functional irrelevance between single vs. double quotes in our YAML
2. Prevalent use of double-quotes in Puppet documentation
3. Similar look-and-feel to other data serialization formats like JSON

Puppetfile

@@ -2,16 +2,16 @@ forge 'https://forge.puppet.com'
 
 # Modules from the Puppet Forge
 # Versions should be updated to be the latest at the time you start
-#mod 'puppetlabs/inifile',     '2.2.1'
-#mod 'puppetlabs/stdlib',      '4.25.1'
-#mod 'puppetlabs/concat',      '4.2.1'
+#mod 'puppetlabs/inifile', '3.0.0'
+#mod 'puppetlabs/stdlib',  '6.0.0'
+#mod 'puppetlabs/concat',  '6.0.0'
 
 # Modules from Git
 # Examples: https://github.com/puppetlabs/r10k/blob/master/doc/puppetfile.mkd#examples
 #mod 'apache',
-#  :git    => 'https://github.com/puppetlabs/puppetlabs-apache',
-#  :commit => 'de290646f97e04b4b8e42c70f6e01e860c394ce7'
+#  git:    'https://github.com/puppetlabs/puppetlabs-apache',
+#  commit: '1b6f89afdde0df7f9433a163d5c4b5328eac5779'
 
 #mod 'apache',
-#  :git    => 'https://github.com/puppetlabs/puppetlabs-apache',
-#  :branch => 'docs_experiment'
+#  git:    'https://github.com/puppetlabs/puppetlabs-apache',
+#  branch: 'docs_experiment'

hiera.yaml

@@ -5,8 +5,8 @@ defaults:
   datadir: "data"
 
 hierarchy:
-  - name: 'Yaml backend'
+  - name: "Yaml backend"
     data_hash: yaml_data
     paths:
       - "nodes/%{trusted.certname}.yaml"
-      - 'common.yaml'
+      - "common.yaml"