Enable no-unused-vars lint

This is the big one. Probably needs thorough review to make sure I
didn't accidentally remove any setInterval or fetch calls.

.eslintrc.js

@@ -50,7 +50,7 @@ module.exports = {
     // Most, if not all, of these rules should eventually be enabled and the code changed. They're disabled so that
     // linting passes.
     rules: {
-        'no-unused-vars': 'off',
+        'no-unused-vars': ['error', {args: 'none'}],
         'no-control-regex': 'off',
         'no-async-promise-executor': 'off',
         'no-inner-declarations': 'off',