chore(package): update eslint-plugin-flowtype to version 5.1.0

Closes #128

Author: greenkeeper[bot]

package.json

@@ -55,7 +55,7 @@
     "eslint-config-prettier": "^4.0.0",
     "eslint-plugin-ava": "^5.1.1",
     "eslint-plugin-babel": "^5.3.0",
-    "eslint-plugin-flowtype": "^3.2.1",
+    "eslint-plugin-flowtype": "^5.1.0",
     "eslint-plugin-import": "^2.14.0",
     "eslint-plugin-jsx-a11y": "^6.1.2",
     "eslint-plugin-react": "^7.12.3",