Update xml answer to work with latest version of xml-json

[`xml-json`](https://github.com/maxogden/xml-json)'s API changed a little when updating to 2.0.0 so the answer to XML is no longer valid, unless the user installs `xml-json@1.0.0` specifically.

This updates the answer to reflect that API change with the added bonus of a cleaner `jsonfilter` call.