Display documentations of demos on the Docs. (#300)

* Display documentations of demos on the Docs.

* Rename the title from `demos` to `Examples`.

demo/demo_cn.rst

+示例
+=====
+
+VisualDL 支持 Python 和 C++ 基于 DL 框架，
+下面是不同平台的一些示例。
+
+.. toctree::
+    :maxdepth: 1
+
+    keras/TUTORIAL_CN.md
+    mxnet/TUTORIAL_CN.md
+    pytorch/TUTORIAL_CN.md
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demo/demo_en.rst

+Examples
+========
+
+VisualDL supports Python and C++ based DL frameworks,
+here are some examples for different platforms.
+
+.. toctree::
+    :maxdepth: 1
+
+    keras/TUTORIAL_EN.md
+    mxnet/TUTORIAL_EN.md
+    pytorch/TUTORIAL_EN.md
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demo/keras/TUTORIAL_CN.md

@@ -92,4 +92,4 @@ class LossHistory(keras.callbacks.Callback):
 
 
 
-完整的演示程序可以在[这里](./keras_mnist_demo.py)下载。
+完整的演示程序可以在[这里](https://github.com/PaddlePaddle/VisualDL/blob/develop/demo/keras/keras_mnist_demo.py)下载。

demo/keras/TUTORIAL_EN.md

@@ -87,4 +87,4 @@ The histograms of the training parameters is as follows:
 <img width="70%" src="https://github.com/daming-lu/large_files/blob/master/keras_demo_figs/keras_histogram.png?raw=true" />
 </p>
 
-The full demonstration code can be downloaded in [here](./keras_mnist_demo.py).
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+The full demonstration code can be downloaded in [here](https://github.com/PaddlePaddle/VisualDL/blob/develop/demo/keras/keras_mnist_demo.py).
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demo/mxnet/TUTORIAL_CN.md

@@ -59,7 +59,7 @@ lenet_model.fit(train_iter,
 
 这样就好了。在MXNet的训练过程中，每一个批次（batch）训练完后，都会调用我们的回调函数来对准确率进行记录。如您所料，随着训练的进行，准确率会不断上升直到95%以上。以下是两个epoch训练过后的准确率走向：
 
-<p align=center><img width="50%" src="./epoch2_small.png" /></p>
+<p align=center><img width="50%" src="https://github.com/PaddlePaddle/VisualDL/blob/develop/demo/mxnet/epoch2_small.png?raw=true" /></p>
 
 ## 用VisualDL展示模型图
 

demo/mxnet/TUTORIAL_EN.md

@@ -61,7 +61,7 @@ That's all. In the training process of MXNet, our callback function is called to
 The rate of accuracy will continue to rise until more than 95%. 
 The following is the accuracy of the two epochs:
 
-<p align=center><img width="50%" src="./epoch2_small.png" /></p>
+<p align=center><img width="50%" src="https://github.com/PaddlePaddle/VisualDL/blob/develop/demo/mxnet/epoch2_small.png?raw=true" /></p>
 
 ## Display the model graph with VisualDL
 

docs/demo

+../demo/
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docs/index_cn.rst

@@ -7,4 +7,5 @@ VisualDL
     首页<README.cn.md>
     quick_start_cn.md
     contribute_code_cn.md
+    demo/demo_cn.rst
     api/visualdl.rst
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docs/index_en.rst

@@ -8,4 +8,5 @@ VisualDL
     quick_start_en.md
     contribute_code_en.md
     how_to_dev_frontend_en.md
+    demo/demo_en.rst
     api/visualdl.rst
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