chore(package): update chai to version 3.4.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -29,7 +29,7 @@
     "imgflo-url": "0.6.0"
   },
   "devDependencies": {
-    "chai": "3.3.0",
+    "chai": "3.4.0",
     "coffee-script": "1.10.0",
     "mocha": "2.5.3"
   },