chapter7 方法名错误
add frontmatters
Merge pull request #32 from kikyous/gh-pages

chapter7 方法名错误
Merge remote-tracking branch 'origin/gh-pages' into gh-pages

* origin/gh-pages:
  chapter7 方法名错误
fix typos
update price of pdf
change number style
update gems version, close #33
add taobao link to epub and mobi ebooks
fix typos in ch2
fix typos in ch3
change footnote refrence mark
add a padding to footnotes