Add CONTRIBUTING.adoc.

CONTRIBUTING.adoc

@@ -0,0 +1,28 @@
+= Contributing to Spring Test for Apache Geode & Pivotal GemFire
+
+Spring Test for Apache Geode & Pivotal GemFire (STDG) is released under the Apache 2.0 license. If you would like to
+contribute something, or simply want to hack on the code this document should help you get started.
+
+== Sign the Contributor License Agreement
+
+If you have not previously done so, please fill out and
+submit the https://cla.pivotal.io/sign/spring[Contributor License Agreement].
+
+== Code of Conduct
+
+Please see our https://github.com/spring-projects/.github/blob/master/CODE_OF_CONDUCT.md[code of conduct]
+
+== Reporting Security Vulnerabilities
+
+Please see our https://github.com/spring-projects/spring-test-data-geode/security/policy[Security policy].
+
+== Using GitHub issues
+
+We use GitHub issues to track bugs and enhancements. If you have a general usage question
+please ask on https://stackoverflow.com[Stack Overflow]. The Spring Data team and the
+broader community monitor the https://stackoverflow.com/tags/spring-session[`spring-session`]
+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.