Update dockerfile tags

paddle/scripts/docker/Dockerfile.cpu

 FROM ubuntu:14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=OFF
 ENV IS_DEVEL=OFF
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.cpu-demo

 FROM ubuntu:14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=OFF
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=ON

paddle/scripts/docker/Dockerfile.cpu-devel

 FROM ubuntu:14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=OFF
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.cpu-noavx

 FROM ubuntu:14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=OFF
 ENV IS_DEVEL=OFF
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.cpu-noavx-demo

 FROM ubuntu:14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=OFF
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=ON

paddle/scripts/docker/Dockerfile.cpu-noavx-devel

 FROM ubuntu:14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=OFF
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.gpu

 FROM nvidia/cuda:7.5-cudnn5-devel-ubuntu14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=ON
 ENV IS_DEVEL=OFF
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.gpu-demo

 FROM nvidia/cuda:7.5-cudnn5-devel-ubuntu14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=ON
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=ON

paddle/scripts/docker/Dockerfile.gpu-devel

 FROM nvidia/cuda:7.5-cudnn5-devel-ubuntu14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=ON
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.gpu-noavx

 FROM nvidia/cuda:7.5-cudnn5-devel-ubuntu14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=ON
 ENV IS_DEVEL=OFF
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.gpu-noavx-demo

 FROM nvidia/cuda:7.5-cudnn5-devel-ubuntu14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=ON
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=ON

paddle/scripts/docker/Dockerfile.gpu-noavx-devel

 FROM nvidia/cuda:7.5-cudnn5-devel-ubuntu14.04
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=ON
 ENV IS_DEVEL=ON
 ENV WITH_DEMO=OFF

paddle/scripts/docker/Dockerfile.m4

 FROM PADDLE_BASE_IMAGE
 MAINTAINER PaddlePaddle Dev Team <paddle-dev@baidu.com>
 COPY build.sh /root/
-ENV GIT_CHECKOUT=develop
+ENV GIT_CHECKOUT=v0.9.0a0
 ENV WITH_GPU=PADDLE_WITH_GPU
 ENV IS_DEVEL=PADDLE_IS_DEVEL
 ENV WITH_DEMO=PADDLE_WITH_DEMO