Add Gemfile and puppet 4 checks

In anticipation of puppet 4, start trying to deal with puppet 4 things
that can be helpfully predicted by puppet lint plugins. Also fix the
lint error caught by the puppet-lint-absolute_classname-check gem.

Change-Id: I5d6563f4b4ae764aba71fb5489c16d6e8602f232

.gitignore

@@ -0,0 +1,2 @@
+Gemfile.lock
+.bundled_gems/

Gemfile

@@ -0,0 +1,30 @@
+source 'https://rubygems.org'
+
+group :development, :test do
+  gem 'puppetlabs_spec_helper', :require => false
+
+  gem 'metadata-json-lint'
+  # This is nice and all, but let's not worry about it until we've actually
+  # got puppet 4.x sorted
+  # gem 'puppet-lint-param-docs'
+  gem 'puppet-lint-absolute_classname-check'
+  gem 'puppet-lint-absolute_template_path'
+  gem 'puppet-lint-trailing_newline-check'
+
+  # Puppet 4.x related lint checks
+  gem 'puppet-lint-unquoted_string-check'
+  gem 'puppet-lint-empty_string-check'
+  gem 'puppet-lint-leading_zero-check'
+  gem 'puppet-lint-variable_contains_upcase'
+  gem 'puppet-lint-spaceship_operator_without_tag-check'
+  gem 'puppet-lint-undef_in_function-check'
+
+  if puppetversion = ENV['PUPPET_GEM_VERSION']
+    gem 'puppet', puppetversion, :require => false
+  else
+    gem 'puppet', '~> 3.0', :require => false
+  end
+
+end
+
+# vim:ft=ruby

manifests/init.pp

@@ -15,7 +15,7 @@
 # == Class: diskimage_builder
 #
 class diskimage_builder () {
-  include pip
+  include ::pip
 
   $packages = [
     'debian-keyring',