富文本|| 图文混排 || NSAttributedString

1 同一段文字中显示不同的颜色
2图片文字混排

参考资料
http://blog.csdn.net/haogaoming123/article/details/46410359
http://blog.csdn.net/huang2009303513/article/details/42237441
http://blog.csdn.net/hero_wqb/article/details/52090189
http://www.cnblogs.com/akforsure/archive/2016/05/19/5363827.html

https://developer.apple.com/reference/foundation/nsattributedstring
http://blog.csdn.net/johnzhjfly/article/details/51134168
http://stackoverflow.com/questions/4217820/convert-html-to-nsattributedstring-in-ios
http://blog.csdn.net/xiaoxiaobukuang/article/details/50411102
NSCharacterSet介绍
http://nshipster.cn/nscharacterset/