Pre-Epoch DateTimes With Fractional Seconds Can't Be Serialized #312

DateTime original = new DateTime(1969, 12, 31, 23, 59, 59);
MessagePackSerializer<DateTime> ser = MessagePackSerializer.Get<DateTime>();
byte[] b = ser.PackSingleObject(original);
Console.WriteLine(string,Join(", ", b));

---> 199, 12, 255, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255

DateTime original = new DateTime(1969, 12, 31, 23, 59, 59).AddTicks(1); // 100ns
MessagePackSerializer<DateTime> ser = MessagePackSerializer.Get<DateTime>();
byte[] b = ser.PackSingleObject(original);

---> System.ArgumentOutOfRangeException : nanoseconds must be non negative value and lessor than 999,999,999.
Parameter name: nanoseconds
   at MsgPack.Timestamp.FromDateTime(DateTime value)
   at MsgPack.Serialization.DefaultSerializers.TimestampDateTimeMessagePackSerializer.PackToCore(Packer packer, DateTime objectTree)
   at MsgPack.Serialization.MessagePackSerializer`1.PackTo(Packer packer, T objectTree)
   at MsgPack.Serialization.MessagePackSerializer`1.PackSingleObjectAsBytes(T objectTree)
   at MsgPack.Serialization.MessagePackSerializer`1.PackSingleObject(T objectTree)