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

Closes #28

Author: greenkeeper[bot]

package.json

@@ -59,7 +59,7 @@
     "eslint-config-problems": "^2.0.0",
     "eslint-plugin-babel": "^5.2.1",
     "eslint-plugin-better": "^0.1.5",
-    "eslint-plugin-flowtype": "^3.0.0",
+    "eslint-plugin-flowtype": "^4.7.0",
     "eslint-plugin-import": "^2.14.0",
     "eslint-plugin-jest": "^22.0.0",
     "eslint-plugin-prettier": "^3.0.0",