优化

【优化】http://www.cocoachina.com/ios/20180817/24599.html
https://mp.weixin.qq.com/s?__biz=MjM5OTM0MzIwMQ==&mid=402351449&idx=1&sn=3ef1c82a123da76a1e899ab70bb5e9f7&scene=1&srcid=0118mcBfdWRqJ8w20WOqmbvh#rd
coretext 优化
http://www.cocoachina.com/ios/20160715/17050.html
异步绘制 texttrue
包体瘦身

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