Added Kali Linux Documentation (#2259)

* Update free-programming-books.md

* Update free-programming-books.md

free-programming-books.md

@@ -1419,6 +1419,7 @@ For resources on Angular, Backbone, D3, Dojo, Ember, Express, jQuery, Knockout,
 * [GNU Autoconf, Automake and Libtool](http://www.sourceware.org/autobook/download.html)
 * [GTK+/Gnome Application Development](http://www.linuxtopia.org/online_books/gui_toolkit_guides/gtk+_gnome_application_development/)
 * [Hardened Linux From Scratch](http://www.linuxfromscratch.org/hlfs/download.html)
+* [Kali Linux: Professional Penetration-Testing Distribution](http://docs.kali.org)
 * [Learn Enough Command Line to Be Dangerous](https://www.learnenough.com/command-line-tutorial) - Michael Hartl
 * [Learning Debian GNU/Linux](http://www.oreilly.com/openbook/debian/book/index.html)
 * [Linux 101 Hacks](http://thegeekstuff.s3.amazonaws.com/files/linux-101-hacks.zip) - Ramesh Natarajan (PDF)