chore(package): update sinon to version 4.2.2

Closes #69

Author: greenkeeper[bot]

package.json

@@ -23,7 +23,7 @@
   "devDependencies": {
     "koop": "2.12.1",
     "nock": "~9.1.1",
-    "sinon": "^2.0.0",
+    "sinon": "^4.2.2",
     "standard": "^9.0.1",
     "supertest": "~3.0.0",
     "tap-spec": "^4.1.1",