Contributing: Link to reporting bugs doc

CONTRIBUTING.md

@@ -12,6 +12,14 @@ etcd is Apache 2.0 licensed and accepts contributions via GitHub pull requests.
 - Fork the repository on GitHub
 - Read the README.md for build instructions
 
+## Reporting Bugs and Creating Issues
+
+Reporting bugs is one of the best ways to contribute. However, a good bug report
+has some very specific qualities, so please read over our short document on
+[reporting bugs](https://github.com/coreos/etcd/blob/master/Documentation/reporting_bugs.md)
+before you submit your bug report. This document might contain links known
+issues, another good reason to take a look there, before reporting your bug.
+
 ## Contribution flow
 
 This is a rough outline of what a contributor's workflow looks like: