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

Closes #7

Author: greenkeeper[bot]

package.json

@@ -7,7 +7,7 @@
     "firebase": "^5.6.0",
     "react": "^16.6.3",
     "react-dom": "^16.6.3",
-    "react-router-dom": "^4.3.1",
+    "react-router-dom": "^5.1.2",
     "react-scripts": "3.1.0",
     "recompose": "^0.30.0",
     "semantic-ui-css": "^2.4.1",