Merge pull request #49 from wenjun1055/master

fix a bug
文章不存在

文章不存在
Merge pull request #51 from zxcvdavid/patch-2

文章不存在（先合并了，等着把函数再给补上）
宏修正

宏修正
Merge pull request #52 from zxcvdavid/patch-3

宏修正
宏修正

宏修正
Merge pull request #53 from zxcvdavid/patch-3

宏修正
Update 1.2.md

细节错误
Merge pull request #54 from wangyunjie/patch-1

Update 1.2.md thx
fix bugs.
Update 2.3.md

修改错别字...
Update 2.2.md

翻译对象的解释
Update 3.2.md

修正
Merge pull request #55 from zs1379/patch-1

Update 2.3.md
Merge pull request #57 from zs1379/patch-3

Update 3.2.md
Merge pull request #56 from zs1379/patch-2

Update 2.2.md 其中有关
修正第二章各节标题
Merge pull request #60 from TopCaver/master

修正第二章各节标题
upgrade chapter 1
upgrade 2.1 and 2.2