Fixed width and height mixup when calculating CGRect center.
Fixed width and height mixup when calculating CGRect center.

CoderJFCK/DACircularProgress,dawangjiaowolaixunshan/DACircularProgress,zhuayi/DACircularProgress,xswm1123/DACircularProgress,drekka/DACircularProgress,wanglongshuai/DACircularProgress,danielamitay/DACircularProgress,mluisbrown/DACircularProgress,jonesgithub/DACircularProgress,sujeking/DACircularProgress,AzenXu/DACircularProgress,sidorov-panda/DACircularProgress,creationst/DACircularProgress,AntiMoron/DACircularProgress