http://scikit-learn.org/stable/modules/ensemble.html#gradient-tree-boosting
https://m.th7.cn/show/10/201702/1106817.html
http://blog.csdn.net/sb19931201/article/details/52577592
http://blog.csdn.net/webzjuyujun/article/details/52116650
http://www.2cto.com/kf/201607/528771.html