1.Fix bug </br>

2.New searchOrganization method</br>
3.New searchFriends method</br>
4.New getDepartmentInfo method</br>
5.New setGroupMemberRoleLevel method</br>

lib/src/enum/group_at_type.dart

@@ -3,4 +3,5 @@ class GroupAtType {
   static const atMe = 1;
   static const atAll = 2;
   static const atAllAtMe = 3;
+  static const groupNotification = 4;
 }