support remind mass message function(send/delete mass message)
TODOs
1. warp EventPushFactory to parse event push message to sub EventPush
class(e.g. SubscribeEventPush, LocationEventPush  and so on);
2. refactor send request to reduce too much similar code.
refactor post body wechat request.
missing commit http util for post body request function.
move toString method to supper class which warp common toString builder.
refactor get wechat request.
replaced wechat url constants  with wechat request enum