http://blog.csdn.net/pipisorry/article/details/52247379
http://webdataanalysis.net/data-analysis-method/data-normalization/
http://www.csuldw.com/2015/11/15/2015-11-15%20normalization/
http://blog.csdn.net/Dream_angel_Z/article/details/49406573
http://blog.csdn.net/ding89629/article/details/7410191
http://sklearn.lzjqsdd.com/modules/preprocessing.html#preprocessing-normalization
http://scikit-learn.org/stable/modules/preprocessing.html#scaling-data-with-outliers