add changelog generator

Gemfile

@@ -27,3 +27,7 @@ end
 group :openstack do
   gem 'kitchen-openstack'
 end
+
+group :tools do
+  gem 'github_changelog_generator', '~> 1'
+end

Rakefile

@@ -0,0 +1,11 @@
+#!/usr/bin/env rake
+# encoding: utf-8
+
+# Automatically generate a changelog for this project. Only loaded if
+# the necessary gem is installed.
+begin
+  require 'github_changelog_generator/task'
+  GitHubChangelogGenerator::RakeTask.new :changelog
+rescue LoadError
+  puts '>>>>> GitHub Changelog Generator not loaded, omitting tasks'
+end