doc contributing

.github/CONTRIBUTING.md

+# Guidelines for Contributing
+
+Thank you for your time on Wechaty.
+
+# Link to Wechaty
+
+Contribute by marketing: Add **Powered by Wechaty** Badge to your Project Homepage:
+
+[![Powered by Wechaty](https://img.shields.io/badge/Powered%20By-Wechaty-green.svg)](https://github.com/wechaty/wechaty)
+
+## Markdown
+
+```markdown
+[![Powered by Wechaty](https://img.shields.io/badge/Powered%20By-Wechaty-green.svg)](https://github.com/wechaty/wechaty)
+```
+
+## Html
+
+```html
+<a href="https://github.com/wechaty/wechaty" target="_blank">
+  <img src="https://img.shields.io/badge/Powered%20By-Wechaty-green.svg" alt="Powered by Wechaty" border="0">
+</a>
+```
+
+# Bug Report
+
+Contribute by feedback, make code robust.
+
+# Feature Request
+
+Contribute by make product suggestion.
+
+# Pull Request
+
+Please:
+ 
+1. submit issue to describe the problem to get start
+1. then send pull request as you need 
+1. and do not forget to reference the issue 
+
+I built wechaty with pleasure because it can help others. help from you for wechaty will be very appreciated by the community.
+
+Cheers!
+
+Huan
+