Clean up and tweak ESLint rules.

Also, refactor ESLint and stylelint config files; now everything will work from our root dir.

js/tests/karma.conf.js

@@ -1,6 +1,5 @@
 /* eslint-env node */
-
-'use strict'
+/* eslint no-process-env: 0 */
 
 module.exports = (config) => {
   const jqueryFile = process.env.USE_OLD_JQUERY ? 'js/tests/vendor/jquery-1.9.1.min.js' : 'assets/js/vendor/jquery-slim.min.js'

js/tests/unit/.eslintrc.json

@@ -11,29 +11,16 @@
     "ecmaVersion": 5,
     "sourceType": "script"
   },
-  "extends": "../.eslintrc.json",
+  "extends": "../../../.eslintrc.json",
   "rules": {
+    "no-console": "off",
     // Best Practices
     "consistent-return": "off",
-    "no-alert": "off",
-    "no-console": "off",
-    "no-empty-function": "off",
-    "no-extend-native": "off",
     "no-magic-numbers": "off",
     "vars-on-top": "off",
 
-    // NodeJS and CommonJS
-    "global-require": "off",
-    "no-process-env": "off",
-    "no-process-exit": "off",
-    "no-sync": "off",
-
     // Stylistic Issues
-    "brace-style": "off",
     "func-style": "off",
-    "max-statements-per-line": "off",
-    "object-curly-newline": "off",
-    "object-property-newline": "off",
     "spaced-comment": "off",
 
     // ECMAScript 6