 if  json file  contain Internationalization   chars   ,  get  exception

```
	json j;
	j["name"] = "中文";

	std::cout << j.dump() << std::endl;
	std::ofstream ofs;
	ofs.open("test.json");
	ofs << j;
	ofs.close();

	std::ifstream ifs("test.json");
	if (!ifs.is_open())
	{
		std::cout << "open error" << std::endl;
		return -1;
	}
	json j2;
	j2 << ifs;
	std::cout << j2.dump() << std::endl;
```
exception at  ```j2 << ifs;```
