Revert "temporarily disable no-underscore-dangle"

This reverts commit 38813b71daa33260c0340a3aa6136af71527e33c.

.eslintrc.json

@@ -1,8 +1,5 @@
 {
   "extends": "airbnb-base",
   "parser": "babel-eslint",
-  "env": { "browser": true },
-  "rules": {
-    "no-underscore-dangle": 0
-  }
+  "env": { "browser": true }
 }