fix link
Merge pull request #56 from lonre/fix-chapter6-link

fix link
Fix typo and indentation in chapter8
Merge pull request #57 from zyuanhong/add_sth

Fix typo and indentation in chapter8
fix a typo error and add a missed snippet of code
Merge pull request #58 from logchi/gh-pages

Fix a typo error and add a missed snippet of code
Fix a order error in chapter8
Email address need to transfer lowercase
Merge pull request #59 from zyuanhong/add_sth

Fix a order error in chapter8
Fix a typo in Chapter 8.1.5
Merge pull request #61 from zyuanhong/add_sth

Fix a typo in Chapter 8.1.5
fix a typo in chapter 5
Merge pull request #62 from perfectfoolish/gh-pages

fix a typo
[Fix] Add missing code in 8.18
Merge pull request #63 from zyuanhong/add_sth

[Fix] Add missing code in 8.18