update django doc (#2313)

free-programming-books.md

@@ -1864,6 +1864,7 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [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 Official Documentation](https://media.readthedocs.org/pdf/django/1.9.x/django.pdf) (PDF) (1.9)
+* [Django Official Documentation](https://media.readthedocs.org/pdf/django/1.10.x/django.pdf) (PDF) (1.10)
 * [Djen of Django](http://agiliq.com/books/djenofdjango/)
 * [Effective Django](http://www.effectivedjango.com) (1.5)
 * [Mastering Django](http://masteringdjango.com) (1.8)