fix(readme): add note to readme about commit message conventions

Author: btford

readme.md

@@ -252,6 +252,8 @@ See the [contributing docs](https://github.com/yeoman/yeoman/blob/master/contrib
 
 When submitting an issue, please follow the [guidelines](https://github.com/yeoman/yeoman/blob/master/contributing.md#issue-submission). Especially important is to make sure Yeoman is up-to-date, and providing the command or commands that cause the issue.
 
+When submitting a PR, make sure that the commit messages match the [AngularJS conventions](https://docs.google.com/document/d/1QrDFcIiPjSLDn3EL15IJygNPiHORgU1_OOAqWjiDU5Y/).
+
 When submitting a bugfix, write a test that exposes the bug and fails before applying your fix. Submit the test alongside the fix.
 
 When submitting a new feature, add tests that cover the feature.