Update CONTRIBUTING to reflect how CI works in our repos (#459)

* Update CONTRIBUTING to reflect how CI works in our repos
* Adjusted wording

Author: TwistedTwigleg

documents/CONTRIBUTING.md

@@ -34,7 +34,8 @@ To send us a pull request, please:
 3. Ensure local tests pass.
 4. Commit to your fork using clear commit messages.
 5. Send us a pull request, answering any default questions in the pull request interface.
-6. Pay attention to any automated CI failures reported in the pull request, and stay involved in the conversation.
+6. Wait for a repository collaborator to look at your pull request, run the automated tests, and review. If additional changes or discussion is needed, a collaborator will get back to you, so please stay involved in the conversation.
+    * Note: pull requests from forks will not run the automated tests without collaborator involvement for security reasons. If you make a pull request and see that the tests are pending, this is normal and expected.
 
 GitHub provides additional document on [forking a repository](https://help.github.com/articles/fork-a-repo/) and
 [creating a pull request](https://help.github.com/articles/creating-a-pull-request/).