Updated free-programming-books.md

Added the Xamarin book under C#

free-programming-books.md

@@ -511,7 +511,6 @@
 * [SVG Essentials](http://commons.oreilly.com/wiki/index.php/SVG_Essentials)
 * [The Quest for Artificial Intelligence: A History of Ideas and Achievements](http://ai.stanford.edu/~nilsson/QAI/qai.pdf) - Nils J. Nilsson (PDF)
 * [Trends Shaping the London Tech Scene](http://www.oreilly.com/programming/free/trends-shaping-the-london-tech-scene.csp) *(Just fill the fields with any values)*
-* [Xamarin Cross-Platform Development Cookbook](https://www.packtpub.com/free-eBook/xamarin-cross-platform-development-cookbook) - George Taskos, Packt. (Just fill the fields with any values)
 
 
 #### MOOC
@@ -886,6 +885,7 @@
 * [Fundamentals of Computer Programming with C#](http://www.introprogramming.info/english-intro-csharp-book/read-online/) - Svetlin Nakov
 * [Introduction to Rx](http://www.introtorx.com)
 * [Threading in C#](http://www.albahari.com/threading/)
+* [Xamarin Cross-Platform Development Cookbook](https://www.packtpub.com/free-eBook/xamarin-cross-platform-development-cookbook) - George Taskos, Packt. (Just fill the fields with any values)
 
 
 ### C++