chore(package): update sinon-chai to version 3.4.0

Closes #51

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "nyc": "^11.3.0",
     "proxyquire": "^1.8.0",
     "sinon": "^4.1.2",
-    "sinon-chai": "^2.14.0"
+    "sinon-chai": "^3.4.0"
   },
   "scripts": {
     "pretest": "npm run lint",