Coursera上Andrew Ng的《机器学习》课程编程作业，采用python来完成
Exercise1：Linear Regression
Exercise2：Logistic Regression
Exercise3：Multi-class Classification and Neural Networks
Exercise4：Neural Networks Learning
Exercise5：Regularized Linear Regression and Bias v.s. Variance
Exercise6：Support Vector Machines
Exercise7：K-means Clustering and Principal Component Analysis
Exercise8：Anomaly Detection and Recommender Systems