"Individual stylesheets must be in the sass directory."

Getting an error and I don't know if or what I do wrong:

> Individual stylesheets must be in the sass directory.
>
> events.js:72
> throw er; // Unhandled 'error' event
> ^
> Error: Compass failed

gulpfile.js:

```
gulp.task('sass', function() {
return gulp.src('assets/sass/**/*')
.pipe(compass({
config_file: '../config.rb',
project: __dirname+'/assets',
css: 'css',
sass: 'sass'
}))
.pipe(gulp.dest('public'));
});
```

config.rb:

```
http_path = '/'
project_path = '../assets'
css_dir = 'css'
sass_dir = 'sass'
scss_dir = 'sass'
javascript_dir = 'scripts'
fonts_dir = 'fonts'
images_dir = 'images'
add_import_path = '../bower_components'
```

file system:

```
|-- assets
| |-- css
| | |-- style.css
| | `-- style.css.map
| |-- fonts
| | |-- varelarnd-regular.otf
| | `-- varelarnd-regular.ttf
| |-- images
| | `-- logo.png
| |-- sass
| | |-- _foundation.scss
| | |-- _foundation_settings.scss
| | `-- style.sass
| `-- scripts
| `-- script.js
|-- bower.json
|-- config.rb
|-- gulpfile.js
`-- public
|-- index.html
|-- script.js
|-- script.min.js
|-- style.css
`-- style.min.css
```

Sass 3.4.0.rc.3
Compass 1.0.0.rc.1 (Polaris)
Gulp 3.8.7
Gulp-compass 1.3.0

Start with gulpfile.js and config.rb, then compare the assets/sass tree and the reported Compass error with the documented directory expectations for gulp-compass. Reproduce the sass task using the listed Sass, Compass, Gulp, and gulp-compass versions; done means the task runs without the directory error and the expected stylesheet is produced.

Written by the indexing model from the issue text.