Update to 3.012
    
    - New upstream release 3.012
    - Use author-independent source URL
    - Classify buildreqs by usage
    - Drop redundant %{?perl_default_filter}
    - Drop recoding of Mail::Message::Field manpage since it has changed to UTF-8
      coding upstream
    - Package README.md too (guide for contributors)
    - Fix permissions verbosely