Move contributing section to its own file

Author: robinst

CONTRIBUTING.md

@@ -0,0 +1,8 @@
+Contributing
+============
+
+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

README.md

@@ -164,11 +164,7 @@ here](src/test/java/org/nibor/autolink/AutolinkEmailTest.java).
 Contributing
 ------------
 
-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
+See CONTRIBUTING.md file.
 
 License
 -------