Fix typo in module name

lib/tools/weightChecker.js

@@ -10,7 +10,7 @@ var debug = require('debug')('ylt:weightChecker');
 var request = require('request');
 var http    = require('http');
 var async   = require('async');
-var Q       = require('Q');
+var Q       = require('q');
 var zlib    = require('zlib');
 
 var WeightChecker = function() {