doc: a little modify

README.md

@@ -52,8 +52,8 @@ cd scikit-opt
 pip install .
 ```
 
-
-### Feature1: UDF
+# Features
+## Feature1: UDF
 
 **UDF** (user defined function) is available now!
 
@@ -133,11 +133,11 @@ my_ga = MyGA(func=demo_func, n_dim=3, size_pop=100, max_iter=500, lb=[-1, -10, -
 best_x, best_y = my_ga.run()
 print('best_x:', best_x, '\n', 'best_y:', best_y)
 ```
-### feature2: GPU computation
+## feature2: GPU computation
  We are developing GPU computation, which will be stable on version 1.0.0  
 An example is already available: [https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_gpu.py](https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_gpu.py)
 
-###  feature3: continue to run
+##  feature3: continue to run
 (New in version 0.3.6)  
 Run an algorithm for 10 iterations, and then run another 20 iterations base on the 10 iterations before:
 ```python

docs/en/README.md

@@ -32,8 +32,8 @@ cd scikit-opt
 pip install .
 ```
 
-
-### Feature1: UDF
+# Features
+## Feature1: UDF
 
 **UDF** (user defined function) is available now!
 
@@ -113,11 +113,11 @@ my_ga = MyGA(func=demo_func, n_dim=3, size_pop=100, max_iter=500, lb=[-1, -10, -
 best_x, best_y = my_ga.run()
 print('best_x:', best_x, '\n', 'best_y:', best_y)
 ```
-### feature2: GPU computation
+## feature2: GPU computation
  We are developing GPU computation, which will be stable on version 1.0.0  
 An example is already available: [https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_gpu.py](https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_gpu.py)
 
-###  feature3: continue to run
+##  feature3: continue to run
 (New in version 0.3.6)  
 Run an algorithm for 10 iterations, and then run another 20 iterations base on the 10 iterations before:
 ```python

docs/zh/README.md

@@ -19,8 +19,8 @@ pip install scikit-opt
 ```
 或者直接把源代码中的 `sko` 文件夹下载下来放本地也调用可以
 
-## 特性
-### 特性1：UDF（用户自定义算子）
+# 特性
+## 特性1：UDF（用户自定义算子）
 
 举例来说，你想出一种新的“选择算子”，如下
 -> Demo code: [examples/demo_ga_udf.py#s1](https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_udf.py#L1)
@@ -99,11 +99,11 @@ best_x, best_y = my_ga.run()
 print('best_x:', best_x, '\n', 'best_y:', best_y)
 ```
 
-### 特性2: GPU 加速
+## 特性2: GPU 加速
 GPU加速功能还比较简单，将会在 1.0.0 版本大大完善。  
 有个 demo 已经可以在现版本运行了: [https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_gpu.py](https://github.com/guofei9987/scikit-opt/blob/master/examples/demo_ga_gpu.py)
 
-### 特性3：断点继续运行
+## 特性3：断点继续运行
 例如，先跑10代，然后在此基础上再跑20代，可以这么写：
 ```python
 from sko.GA import GA