Created by: barrierye

• 添加了支持py2和py3的运行&开发镜像
  • hub.baidubce.com/paddlepaddle/serving:0.2.0 (329M->441M)
  • hub.baidubce.com/paddlepaddle/serving:0.2.0-devel
  • hub.baidubce.com/paddlepaddle/serving:0.2.0-gpu (1.31G->1.53G)
  • hub.baidubce.com/paddlepaddle/serving:0.2.0-gpu-devel
  • dockerhub: barriery/serving:<tag>
• COMPILE文档添加了py3的说明（以py2为例，调整cmake选项即可用py3编译）
• RUN_IN_DOCKER文档添加了py3的说明（以py2为例，可以通过将python更换成python3来用Python3运行相关命令）

fix #436 (closed)