finish translating the frontmatter.md file
Merge remote-tracking branch 'upstream/master'
Merge pull request #40 from liul85/master

Finish translating front matter.md file
删除一段原文；翻译时遗留忘记删除
Merge pull request #41 from wenbing/master

删除一段原文；翻译时遗留忘记删除
translate variables page
Merge pull request #42 from yujingz/master

translate variables page
delete a mis-paste
Merge pull request #43 from yujingz/master

delete a mis-paste