Created 教师偏好获取接口 (markdown)

+###接口地址
+
+>     /teacher_preference/getting
+
+###请求方式
+
+>     get请求
+
+###请求参数
+
+>     无参数
+
+###返回值
+######获取成功
+```json
+{
+  "success": {
+    "id": 5,
+    "userId": 5,
+    "fitGrade": "初一",
+    "publication": "人教2012版",
+    "book": "七上",
+    "difficulty": "1,2,3",
+    "updateTime": "2015-07-21T11:45:32.299+0000"
+  }
+}
+```
+######获取失败情况1
+```json
+{
+  "failed": "该用户未设置偏好"
+}
+```
+######获取失败情况2
+```json
+{
+"failed":"偏好获取失败，存在异常"
+}
+```