Add Django book

free-programming-books.md

@@ -953,6 +953,7 @@ See also [TeX](#tex)
 * [Django by Example for Django 1.5](http://lightbird.net/dbe2/)
 * [Tango With Django](http://www.tangowithdjango.com/book/)
 * [Deploy Django](http://www.deploydjango.com)
+* [The Django Book](http://www.djangobook.com/en/2.0/index.html)
 
 ####Flask
 * [The Flask Mega-Tutorial](http://blog.miguelgrinberg.com/post/the-flask-mega-tutorial-part-i-hello-world)