chore(package): update sinon to version 7.4.1

Closes #19

Author: greenkeeper[bot]

package.json

@@ -28,7 +28,7 @@
 		"mocha-junit-reporter": "^1.17.0",
 		"nyc": "^12.0.2",
 		"rewire": "^4.0.1",
-		"sinon": "^6.0.0",
+		"sinon": "^7.4.1",
 		"sinon-chai": "^3.1.0",
 		"supertest": "^3.1.0",
 		"yarn": "^1.7.0"