0.5

CHANGES:

• Add Async bindings
• Split sync and Lwt variants into separate OPAM packages
• Fix compatibility with OCaml 4.09
• Register callbacks as GC roots
• Port to dune
• Port to OPAM 2 format
• Make dune generate opam files automatically
• Add Changelog to facilitate releases with dune-release
• Depend ob zlib depext instead of explicit package names