Add array support to Swagger::Object and Swagger::Property

[erdnaxeli]

This adds the support of array objects, or array properties. It allows a user to do:

    builder.add(
      Swagger::Object.new(
        "SomethingList",
        "array",
        items: "Something",
      ),
    )

or:

    builder.add(
      Swagger::Object.new(
        "Post",
        "object",
        [
          Swagger::Property.new("id", "integer", "int32", example: 1),
          Swagger::Property.new("comments", "array", items: "Comment"),
        ]
      )
    )

I used refs here but items can also contains a Swagger::Object.

Tests to come.

[icyleaf]

Sorry about no response for a long time.