add PPTs

add ppt for lessions

update license and header

update one line comment

update lesson 8 for header change

update lesson7 for header change

update lesson6 for header

update lesson4 for comment change

update for lesson5 to comments

update test index and comment

update header for lesson5

update train_with_numpy to make calc more clearly

add show_image.py

update to modify header

change import order to save png