code: function addMutationScores(results) {
          _.forOwn(results, function(result) {
              if(_.has(result, 'stats')) {
                  addMutationScores(result);
              }
          });
  
          results.mutationScore = getMutationScore(results.stats);
          return results;
      }
docs: Decorate the results object with the mutation score for each directory.
  
  @param {object} results - (part of) mutation testing results, decorated with mutation stats
  @returns {object} - Mutation test results decorated with mutation scores