Add README to starters

Basic README content plus a short table of community-
contributed additional starters.

See gh-539

Author: Dave Syer

spring-boot-starters/README.adoc

@@ -0,0 +1,17 @@
+Spring Boot Starters are a set of convenient dependency descriptors
+that you can include in your application. You get a one-stop-shop for
+all the Spring and related technology that you need without having to
+hunt through sample code and copy paste loads of dependency
+descriptors. For example, if you want to get started using Spring and
+JPA for database access just include the
+`spring-boot-starter-data-jpa` dependency in your project, and you are
+good to go.
+
+=== Community Contributions
+
+If you create a starter for a technology that is not already in the standard list we can list it here. Just send a pull request for this page.
+
+|===
+| Name | Location
+
+| WRO4J | https://github.com/sbuettner/spring-boot-autoconfigure-wro4j[https://github.com/sbuettner/spring-boot-autoconfigure-wro4j]