v1.6.0 01-21-2019 Paris (France)

• Lost support of OCaml 4.03.0
• Support of OCaml 4.07.0
• Fix tests
• Move to ocurl
• Add materials to test in distribution
• Accept entries with empty author (@thomas-huet)
• Dunify project
• Added Z timezone to comply with RFC 822 and reality (@wictory)
• Accept empty CDATA in copyright field (@sgrove, @dinosaure)