use single quotes around stanza and parameter names

Library/Homebrew/cask/audit.rb

Library/Homebrew/cask/cmd/upgrade.rb

Library/Homebrew/exceptions.rb

Library/Homebrew/extend/on_os.rb

Library/Homebrew/extend/os/linux/on_os.rb

Library/Homebrew/extend/os/mac/on_os.rb

Library/Homebrew/formula_auditor.rb

Library/Homebrew/formula_installer.rb

Library/Homebrew/software_spec.rb

Library/Homebrew/test/cask/audit_spec.rb

Library/Homebrew/utils/ast.rb