yiisoft/yii — pull request #1474 by acorncom (2012-09-26 16:30:19+00:00)
Title: Added in Contributing guidelines to use GitHub's new system

Per GitHub's new Contributing guidelines system, adding this file
will pop up an alert with our guidelines system when people create
an issue or open a pull request.

Reference:
https://github.com/blog/1184-contributing-guidelines