Upgrade build dependencies,

gulpfile.js

@@ -1,5 +1,5 @@
 const gulp     = require('gulp');
-const compiler = require('google-closure-compiler-js').gulp();
+const compiler = require('google-closure-compiler').gulp();
 
 // TODO: Produce multiple files when https://github.com/google/closure-compiler-js/issues/17 resolved
 gulp.task('dist', function () {
@@ -9,9 +9,9 @@ gulp.task('dist', function () {
 		// 'js/jquery.pickmeup.uikit.js'
 	])
 		.pipe(compiler({
-			jsOutputFile : 'pickmeup.min.js',
-			languageIn   : 'ES5',
-			languageOut  : 'ES5'
+			js_output_file : 'pickmeup.min.js',
+			language_in    : 'ES5',
+			language_out   : 'ES5'
 		}))
 		.pipe(gulp.dest('dist'));
 });

package.json

@@ -18,8 +18,8 @@
 	"demo"            : "http://nazar-pc.github.io/PickMeUp",
 	"main"            : "dist/pickmeup.min.js",
 	"devDependencies" : {
-		"google-closure-compiler-js" : "^20160828.0.1",
-		"gulp"                       : "^3.9.1"
+		"google-closure-compiler" : "^20181125.0.1",
+		"gulp"                    : "^4.0.0"
 	},
 	"faircodeId"      : "pd_6bOuEo9pHbWVEqzm9F3K3T"
 }