avoid copy of go dep. from vendor/ for release

tasks/build_task.js

@@ -59,7 +59,7 @@ module.exports = function(grunt) {
     });
     grunt.config('copy.backend_files', {
       expand: true,
-      src: ['conf/defaults.ini', 'conf/sample.ini', 'vendor/**/*', 'scripts/*'],
+      src: ['conf/defaults.ini', 'conf/sample.ini', 'vendor/phantomjs/*', 'scripts/*'],
       options: { mode: true},
       dest: '<%= tempDir %>'
     });