update doc

README.md

@@ -38,7 +38,8 @@ We highly recommend you to run Paddle Serving in Docker, please visit [Run in Do
 
 ```shell
 pip install paddle-serving-client 
-pip install paddle-serving-server
+pip install paddle-serving-server # CPU
+pip install paddle-serving-server-gpu # GPU
 ```
 
 <h2 align="center">Quick Start Example</h2>
@@ -128,6 +129,7 @@ curl -H "Content-Type:application/json" -X POST -d '{"words": "我爱北京天
 - **Description**: 
 ``` shell
 Image classification trained with Imagenet dataset. A label and corresponding probability will be returned.
+Note: This demo needs paddle-serving-server-gpu. 
 ```
 
 - **Download Servable Package**: 

README_CN.md

@@ -39,7 +39,8 @@ Paddle Serving 旨在帮助深度学习开发者轻易部署在线预测服务
 
 ```shell
 pip install paddle-serving-client
-pip install paddle-serving-server
+pip install paddle-serving-server # CPU
+pip install paddle-serving-server-gpu # GPU
 ```
 
 <h2 align="center">快速启动示例</h2>
@@ -167,6 +168,7 @@ curl -H "Content-Type:application/json" -X POST -d '{"words": "我爱北京天
 - **介绍**: 
 ``` shell
 图像分类模型由Imagenet数据集训练而成，该服务会返回一个标签及其概率
+注意：本示例需要安装paddle-serving-server-gpu
 ```
 
 - **下载服务包**: