Update contribution guidelines to describe how we use GitHub issues

CONTRIBUTING.adoc

@@ -5,6 +5,19 @@ something, or simply want to hack on the code this document should help you get
 
 
 
+== Using GitHub issues
+
+We use GitHub issues to track bugs and enhancements. If you have a general usage question
+please ask on http://stackoverflow.com[Stack Overflow]. The Spring Boot team and the
+broader community monitor the http://stackoverflow.com/tags/spring-boot[`spring-boot`]
+tag.
+
+If you are reporting a bug, please help to speed up problem diagnosis by providing as much
+information as possible. Ideally, that would include a small sample project that
+reproduces the problem.
+
+
+
 == Sign the Contributor License Agreement
 Before we accept a non-trivial patch or pull request we will need you to sign the
 https://support.springsource.com/spring_committer_signup[contributor's agreement].