Enforce ES5 or ES6 class for returning value in render function (reac…

…t/require-render-return)

Fixes: standard/standard#1565

eslintrc.json

@@ -22,6 +22,7 @@
     "react/no-danger-with-children": "error",
     "react/no-deprecated": "error",
     "react/no-direct-mutation-state": "error",
+    "react/require-render-return": "error",
     "react/no-unescaped-entities": ["error", {
       "forbid": [">", "}"]
     }],