Update rewire requirement from ^2.5.1 to ^4.0.1

Updates the requirements on [rewire](https://github.com/jhnns/rewire) to permit the latest version.
- [Release notes](https://github.com/jhnns/rewire/releases)
- [Changelog](https://github.com/jhnns/rewire/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jhnns/rewire/commits/v4.0.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -32,7 +32,7 @@
     "html-tag-validator": "^1.5.0",
     "istanbul": "^0.4.3",
     "mocha": "^5.1.0",
-    "rewire": "^2.5.1"
+    "rewire": "^4.0.1"
   },
   "dependencies": {
     "bluebird": "^3.5.2",