Better tests for plugin manager.
Put that Bundle.require statement back.
Refactor the case statement in highlighter for better readability. [ci skip]
Merge pull request #3141 from jekyll/bundle-require-is-borking-pygments

Fix Bundler-integration Plugin Manager
Release :gem: 2.5.2
Add appveyor configuration YAML.
Tweak appveyor.yml.
Tests should run now.
README.markdown: Add AppVeyor badge.