grouped entries in top-level index

Author: Bob Carpenter

README.md

@@ -1,11 +1,21 @@
-## Example-Models
+## Example Models
+
+This repository holds open source Stan models, data simulators, and real data.  There are models translating those found in books, most of the BUGS examples, and some basic examples used in the manual.
+
+#### Books
+
+* [Applied Regression Modeling](https://github.com/stan-dev/example-models/wiki/ARM-Models) (Gelman and Hill 2007)
+* [Bayesian Cognitive Modeling](https://github.com/stan-dev/example-models/tree/master/Bayesian_Cognitive_Modeling) (Lee and Wagenmakers 2014)
+
+#### BUGS examples
+
+- [BUGS Models (volumes 1--3)](https://github.com/stan-dev/example-models/wiki/BUGS-Examples)
+
+#### Basics
 
-This repository holds the following suites of example models:
-- [ARM Models](https://github.com/stan-dev/example-models/wiki/ARM-Models)
 - Basic Distributions
 - Basic Estimators
-- [BUGS Models (volumes 1--3)](https://github.com/stan-dev/example-models/wiki/BUGS-Examples)
 
 ## Licensing
 
-All of the example models are licensed under new BSD license.
+All of the example models are licensed to their author under new BSD license.