chore: fix build, make it compatible with node6

package.json

@@ -43,7 +43,6 @@
   "devDependencies": {
     "@babel/core": "7.5.5",
     "@babel/preset-env": "7.5.5",
-    "del": "5.0.0",
     "eslint": "6.1.0",
     "eslint-config-google": "0.13.0",
     "fancy-log": "1.3.3",
@@ -56,6 +55,7 @@
     "gulp-git": "2.9.0",
     "gulp-jasmine": "4.0.0",
     "jasmine-core": "3.4.0",
+    "rimraf": "3.0.0",
     "rollup": "1.19.4",
     "rollup-plugin-commonjs": "10.0.2",
     "rollup-plugin-node-resolve": "5.2.0",

scripts/clean/index.js

@@ -22,9 +22,11 @@
  * SOFTWARE.
  */
 
-const del = require('del');
+const rimraf = require('rimraf');
 const config = require('../config');
 
-module.exports = function clean() {
-  return del([config.dist]);
+module.exports = function clean(done) {
+  rimraf(config.dist, (err) => (
+    done(err)
+  ));
 };

scripts/lint/index.js

@@ -24,11 +24,18 @@
 
 const path = require('path');
 const gulp = require('gulp');
-const eslint = require('gulp-eslint');
 const log = require('../log');
 const config = require('../config');
 
 module.exports = function lint() {
+  const nodeVersion = process.versions.node;
+  const major = Number(nodeVersion.split('.')[0]);
+  if (major < 8) {
+    log.debug(`Skipping ESLint because of node version compatibility (currenly in used: ${nodeVersion})`);
+    return Promise.resolve();
+  }
+
+  const eslint = require('gulp-eslint');
   const src = [
     path.join(config.root, '*.js'),
     path.join(config.src, '**', '*.js'),