representable uses deprecated multi_json API (MultiJson.load / dump)

[tk0miya]

multi_json renamed its public API in 1.21.0, deprecating the old methods.
ref: https://github.com/sferik/multi_json/blob/v1.21.0/CHANGELOG.md

At present, lib/representable/json.rb calls the legacy multi_json API, which now emits a deprecation warning (will be removed in multi_json 2.0.0):

  def from_json(data, *args)
    data = MultiJson.load(data)     # -> MultiJSON.parse
    from_hash(data, *args)
  end

  def to_json(*args)
    MultiJson.dump to_hash(*args)   # -> MultiJSON.generate
  end

[apotonick]

Thanks 💚 feel free to send a PR, and ping me if you need help!