因为3月1日更新了历史聊天信息拉取，之前的方法不能用了，重新调试遇到了一些问题

按这种格式发送请求 http://a1.easemob.com/1111161019178961/huaxipczd/chatmessages/$2017050817  获取到的消息实体始终是空。按官网文档的说法，我每次只能拉取1个小时的聊天记录？
 
Status: 200
Response Body: {"action":"get","path":"/chatmessages","uri":"http://a1.easemob.com/1111161019178961/huaxipczd/chatmessages/$2017050817","entities":[],"timestamp":1494235827016,"duration":0,"count":0}