refactor: require at least node@6 (drop node@4 support)

Please upgrade node in case you are affected by this. node@6 is the current LTS version

(https://github.com/nodejs/Release#release-schedule).

BREAKING CHANGE: Dropped support of outdated node versions. This package requires at least node@6

now.

.travis.yml

@@ -14,7 +14,6 @@ notifications:
 node_js:
   - 8
   - 6
-  - 4
   - 10
 before_install:
   - npm i -g npm@^6.0.0

lib/rules/template-names.js

@@ -5,6 +5,8 @@
  * See LICENSE file in root directory for full license.
  */
 
+const values = require('../util/values');
+
 const templateProps = new Set([
   'onCreated',
   'onRendered',
@@ -41,7 +43,7 @@ const getErrorMessage = expected =>
 
 module.exports = {
   meta: {
-    schema: [{ enum: Object.values(NAMING_CONVENTIONS) }],
+    schema: [{ enum: values(NAMING_CONVENTIONS) }],
   },
   create: context => ({
     MemberExpression: node => {

lib/util/values.js

@@ -0,0 +1 @@
+module.exports = obj => Object.keys(obj).map(key => obj[key]);

package.json

@@ -60,7 +60,7 @@
     "eslint": ">= 3.7.0 < 5"
   },
   "engines": {
-    "node": ">=4"
+    "node": ">=6"
   },
   "keywords": [
     "eslint",