Add "CoolAid: The Cool 2013 Reference Manual"

Describes the programming language Cool: the Classroom
Object-Oriented Language.

free-programming-books.md

@@ -37,6 +37,7 @@
 * [COBOL](#cobol)
 * [CoffeeScript](#coffeescript)
 * [ColdFusion](#coldfusion)
+* [Cool](#cool)
 * [Coq](#coq)
 * [D](#d)
 * [Dart](#dart)
@@ -526,6 +527,10 @@
 * [Learn CF in a Week](http://learncfinaweek.com/)
 
 
+###Cool
+* [CoolAid: The Cool 2013 Reference Manual](http://www.cs.uwm.edu/~cs654/handouts/cool-manual.pdf) (PDF)
+
+
 ###Coq
 * [Software Foundations](http://www.cis.upenn.edu/~bcpierce/sf/)
 * [Certified Programming with Dependent Types](http://adam.chlipala.net/cpdt/html/toc.html)