http://www.cnblogs.com/PythonHome/archive/2011/11/19/2255459.html
http://www.cnblogs.com/huxi/archive/2010/07/04/1771073.html
http://outofmemory.cn/code-snippet/992/Python-regular-expression-re-module-operation-guide
http://deerchao.net/tutorials/regex/regex.htm#greedyandlazy