fix(package): update date-fns to version 2.13.0

Closes #17

Author: greenkeeper[bot]

package.json

@@ -3,7 +3,7 @@
   "version": "0.2.0",
   "private": true,
   "dependencies": {
-    "date-fns": "^1.30.1",
+    "date-fns": "^2.13.0",
     "firebase": "^5.6.0",
     "react": "^16.6.3",
     "react-dom": "^16.6.3",