Merge pull request #17 from JuliaCN/pdf-dev

add files to generate pdf
Update sidebarintro.html

边栏链接到中文PDF。
2.26 1eb7ca4cc && add note to pdf
2.27 f5e9f3c
chapter2part
fix url
change fonts to song
Merge pull request #24 from JuliaCN/master

update this branch