Drop EL-5 support and use gnupg2 rather than gnupg
    
    - Drop EL-5 support
      - Drop BuildRoot: and Group: tags
      - Drop explicit buildroot cleaning in %install section
      - Drop explicit %clean section
      - BR: perl(Test::YAML::Meta) unconditionally
    - Use gnupg2 rather than gnupg, and explicitly build-require it