Add Eloquent JS to Other Books.

README.md

 * [Understanding Computation](http://computationbook.com) - A book about computation theory by Tom Stuart.
 * [The Tangled Web — Securing Web Applications](http://www.amazon.ca/The-Tangled-Web-Securing-Applications/dp/1593273886) - A book about securing web applications by Michal Zalewski.
 * [Elasticsearch: The Definitive Guide](http://www.elasticsearch.org/guide/) - A guide to working with Elasticsearch by Clinton Gormley and Zachary Tong.
+* [Eloquent JavaScript](http://eloquentjavascript.net/) - A book about JavaScript programming by Marijn Haverbeke.
 
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