Add Django Official Docs.

free-programming-books.md

@@ -1598,6 +1598,8 @@ See also [TeX](#tex)
 
 
 #### Django
+* [Django Official Documentation](https://media.readthedocs.org/pdf/django/1.5.x/django.pdf) (PDF) (1.5)
+* [Django Official Documentation](https://media.readthedocs.org/pdf/django/1.7.x/django.pdf) (PDF) (1.7)
 * [Django by Example](http://www.lightbird.net/dbe/) (1.2)
 * [Django by Example for Django 1.5](http://lightbird.net/dbe2/) (1.5)
 * [Djen of Django](http://agiliq.com/books/djenofdjango/)