增加了cycle_link的循带有hash的环链表的实现，用于存储已发送的apns的message
明天添加已发送数据写入该链表的逻辑，完成response为error时的重发
	modified:   apns/apns_service.go
	new file:   entry/cycle_link.go
	new file:   entry/cycle_link_test.go
	modified:   entry/message.go
	modified:   server/apns_http.go
	renamed:    server/aps_http_handler.go -> server/apns_push_handler.go
	modified:   server/option.go
Merge branch 'master' of https://github.com/blackbeans/go-apns