chore(package): update sinon to version 6.0.0

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
     "npm-run-all": "^4.1.2",
     "nyc": "^11.4.1",
     "prettier": "^1.10.2",
-    "sinon": "^5.0.7",
+    "sinon": "^6.0.0",
     "unexpected": "^10.37.7",
     "unexpected-knex": "^1.2.1",
     "unexpected-sinon": "^10.8.2"