Update Digest-SHA to CPAN version 6.00

Update Digest-SHA to CPAN version 6.00

  [DELTA]

6.00  Fri Dec  8 22:44:44 MST 2017
  - added "tag" option (BSD-style checksums) to shasum
    -- consistent with GNU sha1sum, sha224sum, etc.
    -- thanks to Christopher Tubbs for suggestion
  - modified SHA.pm to use XSLoader
    -- falls back to DynaLoader if necessary
  - decoupled Digest::SHA and Digest::SHA::PurePerl
    -- scripts/tests in each module now fully independent
    -- Digest::SHA::PurePerl to be phased out eventually
      -- past versions will remain available