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

Closes #191

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
     "react-dom": "^16.2.0",
     "react-fontawesome": "^1.6.1",
     "react-redux": "^5.0.6",
-    "react-router": "^4.2.0",
+    "react-router": "^5.1.1",
     "react-router-dom": "^4.2.2",
     "react-rte": "^0.15.0",
     "react-scripts": "1.0.17",