add link to 2nd edition

Author: ChrisMayfield

README.md

@@ -1,13 +1,16 @@
 # ThinkJava
-LaTeX source and code for Think Java, 6th edition.
-Copyright (C) 2016 Allen Downey and Chris Mayfield.
+LaTeX source for Think Java, 1st edition.
+Copyright (c) 2016 Allen Downey and Chris Mayfield.
+
+NOTE: This repository is no longer actively maintained.
+See https://github.com/ChrisMayfield/ThinkJava2 for the 2nd edition of Think Java.
 
 Permission is granted to copy, distribute, and/or modify this work under the
 terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported
 License, which is available at http://creativecommons.org/licenses/by-nc-sa/3.0/.
 
 The original form of this book is the LaTeX source code available from
-http://thinkjava.org and https://github.com/AllenDowney/ThinkJava.
+http://greenteapress.com/wp/think-java/ and https://github.com/AllenDowney/ThinkJava.
 
 The illustrations were drawn using xfig (http://www.xfig.org/) and dia
 (https://wiki.gnome.org/Apps/Dia/). These tools are free and open-source.