It started out as one of 3,000 peer-to-peer lenders in China. In six years, it has become a broad wealth management platform that may raise as much as $5 billion in an international IPO this year. The pace of its growth has been every bit as breathtaking as Tencent’s WeChat or Alibaba’s Alipay, yet few outside China have heard of it. They will. CEO Gregory Gibb tells us why.