[not ready] prepare 4.4 release

This PR tracks all changes before releasing v4.4 of the node-bindings along-side osrm-backend

- [x] merge ~~#72~~ #75.
- [x] Filed PR to fix build script: https://github.com/mapnik/mapnik-packaging/pull/184
- [x] Update this PR
- [x] rebase on master
- [ ] finish osrm-backend v4.4 release
- [ ] Rerun this PR once mapnik-packaging has been updated (and osrm-backend v4.4.0 has been rls'ed)