Created by: barrierye

1. 添加cuda10镜像
2. 编译文档中添加Python依赖安装 pip install -r python/requirements.txt
3. 统一gpu镜像tag，并整理文档：https://github.com/PaddlePaddle/Serving/blob/9feaa523abcdce52fde071cf7997a5342e154c70/doc/DOCKER_IMAGES_CN.md