Bump chai dependency

Author: benvinegar

package.json

@@ -13,7 +13,7 @@
   },
   "main": "src/singleton.js",
   "devDependencies": {
-    "chai": "~1.8.1",
+    "chai": "2.3.0",
     "grunt": "^0.4.5",
     "grunt-browserify": "^4.0.1",
     "grunt-cli": "~0.1.9",