Switch go Gulp 4 for builds

.gitignore

@@ -1,5 +1,6 @@
 # Do not index node.js modules that are used for building
 node_modules
+package-lock.json
 
 # Do not index bower components
 vendor

gulpfile.js

@@ -18,7 +18,7 @@ gulp.task('bower', function(callback) {
         });
 });
 
-gulp.task('prepare-release', ['bower'], function() {
+gulp.task('prepare-release', gulp.series('bower', function() {
     var version = require('./package.json').version;
 
     return eventStream.merge(
@@ -28,14 +28,12 @@ gulp.task('prepare-release', ['bower'], function() {
             .pipe(tar('google-maps-plugin-' + version + '.tar'))
             .pipe(gzip())
     )
-    .pipe(chmod(644))
+    .pipe(chmod(0644))
     .pipe(gulp.dest('release'));
-});
+}));
 
 // Builds and packs plugins sources
-gulp.task('default', ['prepare-release'], function() {
-    // The "default" task is just an alias for "prepare-release" task.
-});
+gulp.task('default', gulp.series('prepare-release'));
 
 /**
  * Returns files stream with the plugin sources.

package.json

@@ -1,13 +1,13 @@
 {
     "version": "1.1.1",
     "devDependencies": {
-        "bower": "~1.3.12",
-        "gulp": "~3.8.10",
+        "bower": "~1.8.8",
+        "gulp": "~4.0.0",
         "event-stream": "~3.1.7",
         "gulp-zip": "~2.0.2",
-        "gulp-tar": "~1.3.1",
+        "gulp-tar": "~3.1.0",
         "gulp-gzip": "~0.0.8",
-        "gulp-chmod": "~1.2.0",
+        "gulp-chmod": "~3.0.0",
         "gulp-rename": "~1.2.0"
     }
-}
+}