fix(package): update react-final-form to version 5.1.2

Closes #29

Author: greenkeeper[bot]

package.json

@@ -12,7 +12,7 @@
     "react": "^16.2.0",
     "react-dom": "^16.2.0",
     "react-emotion": "^9.1.3",
-    "react-final-form": "^3.1.0",
+    "react-final-form": "^5.1.2",
     "react-scripts": "1.1.3"
   },
   "scripts": {