chore(package): update chai to version 4.1.0

Closes #10

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
   },
   "homepage": "https://github.com/msgflo/msgflo-rust#readme",
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.1.0",
     "coffee-script": "^1.10.0",
     "mocha": "^3.2.0",
     "amqplib": "^0.5.1",