v4.0.1

CHANGES:

• Add missing ipaddr-sexp dependency on conduit-async (#385, @anmonteiro)
• Update the link of the documentation (959f57a & #398, reported by @misterfish, @zshipko, @dinosaure)
• Gitignore opam/ even if it is a symlink (#394, @craigfe, @avsm)
• Adapt conduit-lwt-unix to tls.0.14.0 (#396, @hannesm, @dinosaure)