Merge pull request #803 from reitermarkus/heredoc-style

Library/Homebrew/cask/lib/hbc/cli.rb

Library/Homebrew/cask/lib/hbc/cli/uninstall.rb

Library/Homebrew/cask/lib/hbc/container/air.rb

Library/Homebrew/cask/lib/hbc/system_command.rb

Library/Homebrew/cask/test/cask/artifact/uninstall_test.rb

Library/Homebrew/cask/test/cask/artifact/zap_test.rb

Library/Homebrew/cask/test/cask/cli/cat_test.rb

Library/Homebrew/cask/test/cask/cli/create_test.rb

Library/Homebrew/cask/test/cask/cli/search_test.rb

Library/Homebrew/cask/test/cask/cli/uninstall_test.rb

Library/Homebrew/cask/test/cask/dsl_test.rb

Library/Homebrew/cask/test/cask/url_checker_test.rb