We cannot simply rely on [file name lexicographic ordering from broccoli-funnel](https://github.com/trentmwillis/ember-asset-loader/blob/7063ad527e1d00b1a57d64187ed296e02b08c8ce/lib/generate-asset-manifest.js#L29-L34) for generating the asset manifest. Since `ember-asset-loader` respects the ordering in terms of insertion order (which matters) we need to provide a way to configure file order.