Use weak reference for delegate
Use weak reference for delegate

iamyuiwong/MZTimerLabel,yangjie6020/MZTimerLabel,BrianBatchelder/MZTimerLabel,1043426357/MZTimerLabel,fullstackclub/MZTimerLabel,tangwei6423471/MZTimerLabel,mineschan/MZTimerLabel,yunzhongyoulong/MZTimerLabel,KBvsMJ/MZTimerLabel,daixunry/MZTimerLabel,niuxinghua/MZTimerLabel,ListFranz/MZTimerLabel,johnmyqin/MZTimerLabel,sanghavan/MZTimerLabel,Papercloud/MZTimerLabel