SmallGFW基于DFA的敏感词检测和替换模块

smallgfw: 一个基于DFA的敏感词检测和替换模块，用法如doctest所示。

>>> gfw = GFW()
>>> gfw.set(["sexy","girl","love","shit"])#设置敏感词列表
>>> s = gfw.replace("shit!,Cherry is a sexy girl. She loves python.","*")
>>> print s
*!,Cherry is a * *. She *s python. #屏蔽后的效果

>>> gfw = GFW()
>>> gfw.set(["abd","defz","bcz"])
>>> print gfw.check("xabdabczabdxaadefz") #检测敏感词的出现位置
[(1, 3, 'abd'), (5, 3, 'bcz'), (8, 3, 'abd'), (14, 4, 'defz')] #例如，(5, 3, 'bcz')表示下标5之后长度为3的子串