Added the 'Express.js Guide' to the 'Javascript' list.

free-programming-books.md

@@ -917,6 +917,9 @@
 ####Dojo
 * [Dojo: The Definitive Guide](http://chimera.labs.oreilly.com/books/1234000001819/index.html) - Matthew A. Russell
 
+####Express.js
+* [Express.js Guide](https://leanpub.com/express/read) *(Leanpub, by Azat Mardanov)*
+
 ####jQuery
 * [jQuery Succinctly, Syncfusion](http://www.syncfusion.com/resources/techportal/ebooks/jquery) (PDF, Kindle) *(Just fill the fields with any values)*
 * [jQuery Novice to Ninja](http://mediatheque.cite-musique.fr/MediaComposite/Debug/Dossier-Orchestre/ressources/jQuery.Novice.to.Ninja.2nd.Edition.pdf) (PDF)