Update async (0.9.0) and libxmljs (0.12.0)
Update superagent (0.21.0) and superagent-retry (0.5.1) + clean
Drop native integration of iso19139 mapper
Log many things
Improve logging for parse errors
Reimplement harvester with stream API
Add David-DM badge to README.md
Update documentation in README.md
Remove async dependency