Fix quick start (#331)

* Edition of changing eval to test

* first fix of issue 313

* startup

* demo of quickstart

* Fix of quickstart

* remove extra files

* revert cn/mkdocs.yml

* use master cn/mkdocs.yml
Co-authored-by: Nyaochi <later@usopp.net>

cn/docs/code/quick_start/lenet_eval.py

 # lenet_eval.py
 import numpy as np
-import oneflow as flow
+from oneflow.compatible import single_client as flow
 from typing import Tuple
-import oneflow.typing as tp
+from oneflow.compatible.single_client import typing as tp
 
 BATCH_SIZE = 100
 flow.config.enable_legacy_model_io(False)

cn/docs/code/quick_start/lenet_test.py

 import numpy as np
-import oneflow as flow
+from oneflow.compatible import single_client as flow
 from PIL import Image
 import sys
 import os
-import oneflow.typing as tp
+from oneflow.compatible.single_client import typing as tp
 
 BATCH_SIZE = 1
 flow.config.enable_legacy_model_io(False)

cn/docs/code/quick_start/lenet_train.py

 # lenet_train.py
-import oneflow as flow
-import oneflow.typing as tp
+from oneflow.compatible import single_client as flow
+from oneflow.compatible.single_client import typing as tp
 
 BATCH_SIZE = 100
 flow.config.enable_legacy_model_io(False)

cn/docs/quick_start/quickstart_in_3_min.md

@@ -4,7 +4,7 @@
 如果已经安装好了 OneFlow ，可以使用以下命令下载[文档仓库](https://github.com/Oneflow-Inc/oneflow-documentation.git)中的[mlp_mnist.py](https://github.com/Oneflow-Inc/oneflow-documentation/blob/master/cn/docs/code/quick_start/mlp_mnist.py)脚本，并运行。
 
 ```
-wget https://docs.oneflow.org/code/quick_start/mlp_mnist.py #下载脚本
+wget https://docs.oneflow.org/master/code/quick_start/mlp_mnist.py #下载脚本
 python3 mlp_mnist.py #运行脚本
 ```
 
@@ -26,8 +26,8 @@ Epoch [1/20], Loss: 0.3167
 以下是完整代码，我们将对其关键部分进行解读。
 ```python
 # mlp_mnist.py
-import oneflow as flow
-import oneflow.typing as tp
+from oneflow.compatible import single_client as flow
+from oneflow.compatible.single_client import typing as tp
 import numpy as np
 
 BATCH_SIZE = 100