Update .travis.yml to exclude :integration group
Add test-kitchen to Gemfile
Add test-kitchen tasks to Rakefile
Add .kitchen.yml configuration
Add TESTING.md
Add CentOS 6-specific R version
Fix #25 add support for test-kitchen
Fix rubocop offense for using 'then'
Merge pull request #26 from jhx/issue_25_add_support_for_test_kitchen

Issue 25 add support for test kitchen