0.2.1+dune

CHANGES:

• Require OCaml >= 4.08.
• OS.Dir.create fix function result on existing files. It returned
  non-sensical results. The function now errors as it should
  be. Thanks to Léo Andrès for the report.
• OS.Dir.create fix function returning false instead of
  true when the directory is created with ~path:false.
  Thanks to Léo Andrès for the report and patch.
• OS.File.read support for reading character devices and named
  pipes. Thanks to Rizo Isrof for the patch.