add more python related doc
add bib
	modified:   bib.bib
	modified:   learn-py-from-django.tex
	modified:   main.tex
	modified:   new-cmd.tex
Merge branch 'writing'

Conflicts:
	notes/bib.bib
	notes/learn-py-from-django.tex
	notes/main.tex

	modified:   bib.bib
	modified:   learn-py-from-django.tex
	modified:   new-cmd.tex