自定义alertview，支持多种视图定义
1.实例化AlertView CVAlertView *alertView = [[CVAlertView alloc] initWithTitle:@"新功能" message:@"1.支持iOS9 \n 2.增加丰富的表情 \n 3.peter 改进了很多bug" cancelButtonTitle:@"确认" otherButtonTitle:nil otherButtonAction:nil];
2.调用showAlertView [alertView showAlertView];
