build(gulp): upgrade to Gulp 4

gulpfile.js

@@ -19,28 +19,28 @@ gulp.task('prepack', function(cb){
   webpack('webpack.prepack.config.js', cb);
 });
 
-gulp.task('webpack-cordova', ['prepack'], function(cb){
+gulp.task('webpack-cordova', gulp.series('prepack', function(cb){
   webpack('webpack.cordova.config.js', cb);
-});
+}));
 
-gulp.task('dist', ['prepack'], function(cb){
+gulp.task('dist', gulp.series('prepack', function(cb){
   webpack('webpack.library.config.js', cb);
-});
+}));
 
-gulp.task('remap', ['webpack-cordova'], function () {
+gulp.task('remap', gulp.series('webpack-cordova', function () {
   return gulp.src(['dist/plugin.min.js', 'dist/www.min.js'])
   .pipe(insert.prepend(remap))
   .pipe(gulp.dest('dist'));
-});
+}));
 
-gulp.task('plugin', ['remap'], function () {
+gulp.task('plugin', gulp.series('remap', function () {
   return gulp.src(['dist/plugin.min.js'])
   .pipe(gulp.dest('src/browser'));
-});
+}));
 
-gulp.task('www', ['remap'], function () {
+gulp.task('www', gulp.series('remap', function () {
   return gulp.src(['dist/www.min.js'])
   .pipe(gulp.dest('www'));
-});
+}));
 
-gulp.task('default', ['dist', 'plugin', 'www']);
+gulp.task('default', gulp.series('dist', 'plugin', 'www'));

package.json

@@ -61,7 +61,7 @@
     "conventional-changelog-cli": "^1.2.0",
     "cz-conventional-changelog": "3.3.0",
     "express": "^4.14.0",
-    "gulp": "^3.9.1",
+    "gulp": "^4.0.2",
     "gulp-insert": "^0.5.0",
     "husky": "^0.13.1",
     "jshint": "^2.9.2",