Update to 1.2.1
    
    Appart from updating bats to v1.2.1 this also:
    
    - adds a new (build) dependency - GNU Parallel
    - includes a new upstream test in %check (parallel.bats)
    - removes the sed in %prep because shebang mangling is done
      automatically
    - changes the URL for Source0 so that it does not rely on hardcoded
      commit