chore(package): update sinon to version 7.4.2

Closes #49

Author: greenkeeper[bot]

package.json

@@ -54,7 +54,7 @@
     "prop-types": "^15.6.0",
     "react": "^16.2.0",
     "react-dom": "^16.2.0",
-    "sinon": "^6.0.0"
+    "sinon": "^7.4.2"
   },
   "peerDependencies": {
     "prop-types": "^15.6.0",