BVAL-464 Adding CONTRIBUTING.md file

Author: gunnarmorling

CONTRIBUTING.md

@@ -0,0 +1,16 @@
+Guidelines for contributing to Bean Validation
+====
+
+Contributions from the community are essential in keeping Bean Validation strong and successful.
+
+Please see the following pages to learn more about contributing to the Bean Validation spec, its API, TCK and website:
+
+* [General contribution guide](http://beanvalidation.org/contribute/)
+* [Contributing to the specification](http://beanvalidation.org/contribute/specification/)
+* [Contributing to the API and the TCK](http://beanvalidation.org/contribute/coding)
+* [Contributing to the website](http://beanvalidation.org/contribute/site)
+
+Before working on a feature for a long time, it is recommended to discuss the suggested change,
+e.g. by sending a mail to the [beanvalidation-dev](http://lists.jboss.org/pipermail/beanvalidation-dev/) mailing list.
+If there's agreement on a given change and this is your first pull request for Bean Validation,
+please sign the [Contributor License Agreement](https://cla.jboss.org/) for the "Bean Validation" project.