Use current babel/eslint integration

Fixes these `npm install` warnings:

> deprecated babel-eslint@10.1.0: babel-eslint is now @babel/eslint-parser. This package will no longer receive updates.
> deprecated eslint-loader@4.0.2: This loader has been deprecated. Please use eslint-webpack-plugin

.eslintrc.json

@@ -5,7 +5,7 @@
         "es6": true
     },
     "extends": ["eslint:recommended", "standard", "standard-react"],
-    "parser": "babel-eslint",
+    "parser": "@babel/eslint-parser",
     "parserOptions": {
         "ecmaVersion": "7",
         "ecmaFeatures": {