Update README.md (#66)

* Update README.md
* put jpeg center

README.md

+<div align='center'>
+  <img src='./docs/imgs/ppgan.jpg'>
+</div>
+
 简体中文 | [English](./README_en.md)
 
 # PaddleGAN
@@ -5,20 +9,32 @@
 PaddleGAN 是一个基于飞桨的生成对抗网络开发工具包.
 
 ### 图片变换
-![](./docs/imgs/A2B.png)
-![](./docs/imgs/B2A.png)
+<div align='center'>
+  <img src='./docs/imgs/A2B.png'>
+</div>
+<div align='center'>
+  <img src='./docs/imgs/B2A.png'>
+</div>
 
 ### 妆容迁移
-![](./docs/imgs/makeup_shifter.png)
+<div align='center'>
+  <img src='./docs/imgs/makeup_shifter.png'>
+</div>
 
 ### 老视频修复
-![](./docs/imgs/color_sr_peking.gif)
+<div align='center'>
+  <img src='./docs/imgs/color_sr_peking.gif'>
+</div>
 
 ### 超分辨率
-![](./docs/imgs/sr_demo.png)
+<div align='center'>
+  <img src='./docs/imgs/sr_demo.png'>
+</div>
 
 ### 动作驱动
-![](./docs/imgs/first_order.gif)
+<div align='center'>
+  <img src='./docs/imgs/first_order.gif'>
+</div>
 
 特性:
 

README_en.md

+<div align='center'>
+  <img src='./docs/imgs/ppgan.jpg'>
+</div>
+
 English | [简体中文](./README.md)
 
 # PaddleGAN
@@ -5,21 +9,35 @@ English | [简体中文](./README.md)
 PaddleGAN is an development kit of Generative Adversarial Network based on PaddlePaddle.
 
 ### Image Translation
-![](./docs/imgs/A2B.png)
-![](./docs/imgs/B2A.png)
+<div align='center'>
+  <img src='./docs/imgs/A2B.png'>
+</div>
+<div align='center'>
+  <img src='./docs/imgs/B2A.png'>
+</div>
+
 
 ### Makeup shifter
-![](./docs/imgs/makeup_shifter.png)
+<div align='center'>
+  <img src='./docs/imgs/makeup_shifter.png'>
+</div>
+
 
 ### Old video restore
-![](./docs/imgs/color_sr_peking.gif)
+<div align='center'>
+  <img src='./docs/imgs/color_sr_peking.gif'>
+</div>
 
 ### Super resolution
 
-![](./docs/imgs/sr_demo.png)
+<div align='center'>
+  <img src='./docs/imgs/sr_demo.png'>
+</div>
 
 ### Motion driving
-![](./docs/imgs/first_order.gif)
+<div align='center'>
+  <img src='./docs/imgs/first_order.gif'>
+</div>
 
 Features: