Change README, change ipynb to py

Author: Tony_Tian_1122

README.md

@@ -19,4 +19,6 @@ t_test(data1, data2).paired_sample_t_test()
 ```
 
 # ML Models
+ml_regression.py: contain 5 most popular machine learning regression functions, implemented using scikit-learn standard library
+unsupervised_clustering.py: contain most popular unsupervised learning clustering functions, implemented using scikit-learn standard library
 # DL Models