chore(package): update chai to version 4.1.2

Closes #83

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "request": "~2.81.0"
   },
   "devDependencies": {
-    "chai": "~4.0.1",
+    "chai": "~4.1.2",
     "coffee-script": "~1.12.5",
     "espower-coffee": "~1.1.0",
     "hubot": ">= 2.7",