Use new theme
rm _themes submodule
rm the _themes
switch to hit9
update theme
update todo
remove submodule flask_small
remove submodule `flask theme for sphinx`
use new theme `rux`
two new post
fix typo & format.
Merge pull request #6 from TheLoverZ/typo_fix

fix typo & format.
update post
fix build instrctions
update post
Update REAME.md
update post
update post
Merge pull request #7 from skyline75489/master

更新《Python魔法方法指南》，修改“一起编写”部分
update post