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

Closes #131

Author: greenkeeper[bot]

package.json

@@ -132,7 +132,7 @@
     "react-dom": "^16.0.0",
     "react-hot-loader": "^4.0.0",
     "react-redux": "^5.0.7",
-    "react-router": "^4.1.2",
+    "react-router": "^5.1.2",
     "react-router-dom": "^4.1.2",
     "react-router-redux": "^5.0.0-alpha.9",
     "redux": "^3.7.2",