Updated 课程分类信息查询 (markdown)

-etc
+接口返回值为：
+```json
+[
+  {
+    "id": 1,
+    "path": 100,
+    "name": "教材"
+  },
+  {
+    "id": 2,
+    "path": 100100,
+    "name": "七年级上"
+  },
+  {
+    "id": 3,
+    "path": 100100100,
+    "name": "Unit 1"
+  },
+  {
+    "id": 4,
+    "path": 100100101,
+    "name": "Unit 2"
+  }
+]
+```