fix(package): update react-router to version 5.1.2

Closes #757

Author: greenkeeper[bot]

packages/admin-ui/package.json

@@ -40,7 +40,7 @@
     "react-jss": "^8.4.0",
     "react-redux": "^5.0.7",
     "react-redux-loading-bar": "^4.1.0",
-    "react-router": "^4.3.1",
+    "react-router": "^5.1.2",
     "react-router-dom": "^4.2.2",
     "react-router-redux": "^5.0.0-alpha.9",
     "react-rte": "^0.16.1",