用环信的聊天界面，想要更改聊天的气泡样式和时间的显示方式

[[EaseBaseMessageCell appearance] setSendBubbleBackgroundImage:[[UIImage imageNamed:@"chat_sender_bg"] stretchableImageWithLeftCapWidth:5 topCapHeight:35]];
    [[EaseBaseMessageCell appearance] setRecvBubbleBackgroundImage:[[UIImage imageNamed:@"chat_receiver_bg"] stretchableImageWithLeftCapWidth:35 topCapHeight:35]];
设置聊天气泡