libevent：
http://www.wangafu.net/~nickm/libevent-book/01_intro.html
https://github.com/ariya/phantomjs
https://github.com/binux/pyspider
http://sourcecodebrowser.com/libevent/2.0.3-alpha/evbuffer-internal_8h.html
http://blog.csdn.net/luotuo44/article/details/38403241
http://my.oschina.net/liting/blog/372484