chore(package): update sinon to version 6.0.0

Closes #29

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "@types/node": "^10.0.3",
     "@types/sinon": "^4.3.0",
     "jest": "^22.4.3",
-    "sinon": "^4.5.0",
+    "sinon": "^6.0.0",
     "standard-version": "^4.3.0",
     "ts-jest": "^22.4.2",
     "typescript": "^2.8.1"