gulp-compass is not working in the gulp's stream paradigm

gulp-compass uses the config `css` and `scss` to determine the input files and output files, but a more-gulp way should be:

```
gulp.src('path/to/*.scss')
.pipe(compass({ /* settings other than input and output folder */)
.pipe(gulp.dest('path/to/.css')
```

I highly recommend gulp-compass change to this paradigm.

Start by reviewing gulp-compass's current handling of the `css` and `scss` configuration and its gulp stream entry point. The change is done when input and output paths come from `gulp.src` and `gulp.dest`, while the plugin accepts other Compass settings through its options.

Written by the indexing model from the issue text.