ESLint config clean up (vuejs-templates#1093)

* Remove unnecessary quotes from .eslintrc.js

Since we're using .js config we are already abusing JS object literal brevity in other fields. Unquoting these fields brings consistency to ESLint config.

* ESLint config is more explicit

* Remove redundant rule for ESLint Standard JS
Remove ESLint 'arrow-parens' rule for StandardJS. StandardJS don't define this rule. So it's redundant to specify it's ignorance explicitly.

Author: exarus

template/.eslintrc.js

@@ -22,34 +22,32 @@ module.exports = {
   ],
   {{#if_eq lintConfig "airbnb"}}
   // check if imports actually resolve
-  'settings': {
+  settings: {
     'import/resolver': {
-      'webpack': {
-        'config': 'build/webpack.base.conf.js'
+      webpack: {
+        config: 'build/webpack.base.conf.js'
       }
     }
   },
   {{/if_eq}}
   // add your custom rules here
-  'rules': {
+  rules: {
     {{#if_eq lintConfig "standard"}}
-    // allow paren-less arrow functions
-    'arrow-parens': 0,
     // allow async-await
-    'generator-star-spacing': 0,
+    'generator-star-spacing': 'off',
     {{/if_eq}}
     {{#if_eq lintConfig "airbnb"}}
     // don't require .vue extension when importing
     'import/extensions': ['error', 'always', {
-      'js': 'never',
-      'vue': 'never'
+      js: 'never',
+      vue: 'never'
     }],
     // allow optionalDependencies
     'import/no-extraneous-dependencies': ['error', {
-      'optionalDependencies': ['test/unit/index.js']
+      optionalDependencies: ['test/unit/index.js']
     }],
     {{/if_eq}}
     // allow debugger during development
-    'no-debugger': process.env.NODE_ENV === 'production' ? 2 : 0
+    'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off'
   }
 }