Created 依据教师年级获取课程一级分类接口 (markdown)

+###接口地址
+
+>     /teacher/catalogs/getting
+
+###请求方式
+
+>     get请求
+
+###请求参数
+
+>     "fit_grade":"初一"
+>     年级fit_grade为单选
+
+###返回值
+######正常返回值
+```json
+{
+  "success": [
+    "教材",
+    "文章",
+    "发音",
+    "对话",
+    "词汇",
+    "测验",
+    "私人定制"
+  ]
+}
+```
+
+######异常返回值
+```json
+{
+  "failed": "教师选择的年级存在错误"
+}
+```