Exclusion Doesn't Work in passthrough

I've tried everything I can to get the plugin to NOT add in a certain subfolder of my project to the concat'd stylesheet output, but no no avail. Here's my config from `ember-cli-build`:

```
sassOptions: {
includePaths: [],
onlyIncluded: true,
passthrough: {
include: ['app/styles/**/*','node_modules/**/**'],
exclude: ['app/sfcs/*'],
annotation: 'Funnel (styles, no SFC styles)'
}
},
```

(The `node_modules` inclusion above is an attempt to replicate the default tree, because these options cause my `app.scss` to fail on ` @import "ember-cli-bootstrap-4/bootstrap";` Eventually, I got bootstrap working again with `@import "../../node_modules/bootstrap/scss/bootstrap";` but I digress.)

I thought that by setting `includePaths:[]` and `onlyInclude: true` would cause the plugin to bypass generating it's own inclusion tree (which is what the source seems to say), and then I could give the `Funnel` my own opts. According to docs, `exclude` takes precedence over `include` - but even with these options set, I **still** see the styles in `app/sfcs/` present in the output.

Any advice on how to just exclude one folder from the compiled output...?