chore(package): update chai to version 4.0.2

Closes #13

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
   },
   "devDependencies": {
     "bootprint": "^1.0.0",
-    "chai": "^3.5.0",
+    "chai": "^4.0.2",
     "ghooks": "^2.0.0",
     "m-io": "^0.5.0",
     "mocha": "^3.2.0",