Expand Contributing section

Author: robinst

README.md

@@ -113,7 +113,11 @@ Also see [test cases](src/test/java/org/nibor/autolink/AutolinkEmailTest.java).
 Contributing
 ------------
 
-Pull requests welcome :)!
+Pull requests, issues and comments welcome ☺. For pull requests:
+
+* Add tests for new features and bug fixes
+* Follow the existing style (always use braces, 4 space indent)
+* Separate unrelated changes into multiple pull requests
 
 License
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