Cleanup pref.'s style and add comment.

Former-commit-id: ab01044b50ef4a6d447e3e937c31cf5747b3113b

perf/perf.js

@@ -75,6 +75,7 @@
       } else {
         console.log(fastest + ' is the fastest.');
       }
+      // add score adjusting for maring of error
       score.lodash += Math.floor(1 / (this[0].stats.mean + this[0].stats.moe));
       score.underscore += Math.floor(1 / (this[1].stats.mean + this[1].stats.moe));