chore(package): update react-router to version 5.1.1

Closes #303

Author: greenkeeper[bot]

package.json

@@ -58,7 +58,7 @@
     "nyc": "^11.1.0",
     "react": "^16.3.0",
     "react-dom": "^16.3.0",
-    "react-router": "^3.0.4",
+    "react-router": "^5.1.1",
     "react-test-renderer": "^15.6.1",
     "sinon": "2.3.8",
     "webpack": "3.3.0",