Updated 教师偏好设置接口 (markdown)

 #### 接口地址
 
-  >/teacher_preference/setting
+  >     /teacher_preference/setting
 
 ####请求方式
 
-  >POST请求 
+  >     POST请求 
 
 ####参数格式
 
-  - "fit_grade":"初一"
-  - "difficulty":"1"
-  - "relation_material":"人教2012版-七上"
+  >     - "fit_grade":"初一"
+  >     - "difficulty":"1"
+  >     - "relation_material":"人教2012版-七上"
 
 ####返回值
-  ######设置成功
-   ```json
 
-   "偏好设置": "success"
+######设置成功
 
-  ######设置失败
+   ```json
+  {
+   "偏好设置": "success"
+  }
+```
+######设置失败
 
+```json
+  {
    "偏好设置": "failed"
-
-
+  }
+```