Add benchmark task to npm

Author: Ruben Bridgewater

benchmarks/multi_bench.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var redis = require("./index"),
+var redis = require("../index"),
     metrics = require("metrics"),
     num_clients = parseInt(process.argv[2], 10) || 5,
     num_requests = 20000,

package.json

@@ -12,6 +12,7 @@
   "scripts": {
     "coveralls": "nyc report --reporter=text-lcov | coveralls",
     "coverage": "nyc report --reporter=html",
+    "benchmark": "node benchmarks/multi_bench.js",
     "test": "nyc ./node_modules/.bin/_mocha ./test/*.js ./test/commands/*.js ./test/parser/*.js --timeout=8000",
     "pretest": "optional-dev-dependency hiredis",
     "posttest": "jshint ."