http://blog.csdn.net/scruelt/article/details/78997697
https://github.com/fengdu78/Coursera-ML-AndrewNg-Notes/blob/master/code/ex1-linear regression/ML-Exercise1.ipynb
https://github.com/HuangCongQing/MachineLearning_Ng
https://github.com/yoyoyohamapi/mit-ml