Added "Hacknot: Essays on Software Development"

free-programming-books.md

@@ -379,6 +379,7 @@
 * [97 Things Every Programmer Should Know - Extended](https://leanpub.com/97-Things-Every-Programmer-Should-Know-Extended)
 * [A Mathematical Theory of Communication](http://cm.bell-labs.com/cm/ms/what/shannonday/paper.html) by Claude E.Shannon
 * [Asterisk™: The Definitive Guide](http://asteriskdocs.org/en/3rd_Edition/asterisk-book-html-chunk/index.html)
+* [Hacknot: Essays on Software Development](http://www.lulu.com/shop/ed-johnson/hacknot-essays-on-software-development/ebook/product-17544641.html) - Ed Johnson
 * [How to Think Like a Computer Scientist](http://openbookproject.net/thinkcs/) -  Peter Wentworth, Jeffrey Elkner, Allen B. Downey, and Chris Meyers
 * [I Am a Bug](http://www.amibug.com/iamabug/p01.html)
 * [Learn to Program](http://pine.fm/LearnToProgram/)