chore(package): update eslint-plugin-flowtype to version 4.7.0

Closes #42

Author: greenkeeper[bot]

package.json

@@ -53,7 +53,7 @@
     "eslint": "^5.6.1",
     "eslint-config-react-app": "^4.0.0",
     "eslint-loader": "2.1.2",
-    "eslint-plugin-flowtype": "^3.9.1",
+    "eslint-plugin-flowtype": "^4.7.0",
     "eslint-plugin-import": "^2.14.0",
     "eslint-plugin-jsx-a11y": "^6.1.2",
     "eslint-plugin-react": "^7.11.1",