1.1.0+dune

CHANGES:

• Ptime.of_rfc3339 timezone offset parsing. Be even more lenient
  in non-strict parsing mode: allow hhmm and hh timezone offsets.
  (strict is hh:mm). Allows to parse an even larger subset of
  ISO 8601 than RFC 3339 (dbuenzli#31).
• Add Ptime.{to,of}_year. Less costly than extracting the first
  component of Ptime.to_date_time. Useful for example to find
  out which DST rules a timestamp is subjected to for rendering.
• Add ?tz_offset_s optional argument to Ptime.{of,to}_date (dbuenzli#32).
• Add Ptime.weekday_num. An integer is often more convenient
  than the enum value of Ptime.weekday (dbuenzli#30).
• Add Ptime.rfc3339_string_error convenience function.
• Use the new js_of_ocaml META ocamlfind standard to link
  JavaScript stubs (dbuenzli#28).
• No longer install interfaces in the ptime.clock package,
  this package is now empty.