Comments option doesn't work

```
gulp.src(scssSources)
    .pipe(compass({
      comments: true,
      css: env + '/assets', 
      sass: 'development/assets/scss',
    })
    .on('error', gutil.log))
    .pipe(gulp.dest(output_dir + 'assets/'))
```

Comments won't appear in the output compiled file.
