Add RexEgg

free-programming-books.md

@@ -565,6 +565,7 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
 * [Learn Regex The Hard Way](http://regex.learncodethehardway.org/book/) - Zed. A. Shaw
 * [The Bastards Book of Regular Expressions: Finding Patterns in Everyday Text](https://leanpub.com/bastards-regexes) - Dan Nguyen
 * [The 30 Minute Regex Tutorial](http://www.codeproject.com/Articles/9099/The-Minute-Regex-Tutorial) - Jim Hollenhorst
+* [RexEgg](http://www.rexegg.com/)
 
 
 #### Reverse Engineering