Initial commit
First version of chap6

Please have it reviewed and pull request, thank you!
Initial commit
the first time commit file.
seconde commit
Change tables into snapshots from original book
delete html preview, remove /User/.../chap6
add back html file, and solve picture path problem
Add img folder to store images used in chap6.md
2.commit test
commit the structure
section one
Merge pull request #3 from kfeng123/develop

almost complete
Merge pull request #1 from AndrewHub/gh-pages

chap6翻译初稿
Reviewed by Lynn

增加了复习内容
Merge branch 'gh-pages' of https://github.com/johnstart/data-science into gh-pages
Merge pull request #4 from AndrewHub/gh-pages

Reviewed by Lynn
add image for section 1
Merge branch 'master' into develop
First page of chp7 by ripe