3.0.0

CHANGES:

Major version that breaks code for every user. Sorry!

Breaking

• Generated code now always fits into 2 files: code
  for foo.proto is produced in foo.ml and foo.mli.
  This follows a fairly large internal refactor that enables
  a plugin architecture internally (which facilitated codegen for
  services).
  All encoder/decoder functions also have a new name now,
  so that they don't collide inside the same file.
• CLI flags now use --this-style rather than -this-style
• Bump minimal OCaml version to 4.08

Performance

• encode probotufs backward, which means we can write directly
  into a single buffer (which is not possible in a forward mode
  because sub-messages require an unknown amount of prefix space
  to write their size as a varint)
• add C stubs for pbrt
• use Bytes functions to read/write fixed size integers
• inlining annotations
• more benchmarks, helping optimization overall
• reduce allocations drastically, by having the generated code
  create fewer closures

Services

• add pbrt_services runtime library
• generate code for service statements. This is a big feature
  for users who want to implement RPC systems using protobuf.
  The generated code is agnostic to whatever RPC implementation
  will use it, it only packs together RPC method names and path
  with the relevant encoders/decoders. Services require
  both JSON and binary encoders/decoders to be present.

JSON

• migrate pbrt_yojson into the main ocaml-protoc repo
• JSON runtime support for empty messages
• Add support for bytes in JSON encoding
• Add support for encoding and decoding maps in JSON

Other features and fixes

• add --make flag to generate make functions that take fewer
  optional arguments. This helps preventing the user from
  forgetting important arguments when they're encoding to protobuf.
  Arguments actually marked as optional in the .proto file
  are still optional.
• Support maps/lists in options
• add Pbrt.Decoder.of_substring
• Allow options to be named like (validate.rules).message.required
• support code generation for empty messages
• Empty proto file is a valid proto as well

Testing

• expect-style tests for parser
• Tests for option parsing
• Test demonstrating parse error printing