add index.md
Merge pull request #47 from riverfeng/gh-pages

finished index.md
Add Wearable Actrice
Compile book
commit book
Merge pull request #48 from pedant/gh-pages

merge for jni-tips part
Update readme
multi section without link url
Merge pull request #49 from Andrwyw/gh-pages

multi section  未添加链接，待修改校正。