code: function time(cmd, runs, runNumber, results, cb) {
      var start = process.hrtime();
      exec(cmd, { silent: true }, function() {
          var diff = process.hrtime(start),
              actual = diff[0] * 1e3 + diff[1] / 1e6; // ms
  
          results.push(actual);
          echo("Performance Run #" + runNumber + ":  %dms", actual);
          if (runs > 1) {
              time(cmd, runs - 1, runNumber + 1, results, cb);
          } else {
              return cb(results);
          }
      });
  }
docs: Calculates the time for each run for performance
  @param {string} cmd cmd
  @param {int} runs Total number of runs to do
  @param {int} runNumber Current run number
  @param {int[]} results Collection results from each run
  @param {function} cb Function to call when everything is done
  @returns {int[]} calls the cb with all the results
  @private