Move "Contributing" section into dedicated document for better GitHub…

… integration

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

CONTRIBUTING.textile

@@ -0,0 +1,14 @@
+h2. How to contribute
+
+If you find what looks like a bug:
+
+# Search the "mailing list":http://groups.google.com/group/delayed_job to see if anyone else had the same issue.
+# Check the "GitHub issue tracker":http://github.com/collectiveidea/delayed_job/issues/ to see if anyone else has reported issue.
+# If you don't see anything, create an issue with information on how to reproduce it.
+
+If you want to contribute an enhancement or a fix:
+
+# Fork the project on github.
+# Make your changes with tests.
+# Commit the changes without making changes to the Rakefile or any other files that aren't related to your enhancement or fix
+# Send a pull request.

README.textile

@@ -275,18 +275,3 @@ You can invoke @rake jobs:clear@ to delete all jobs in the queue.
 h2. Mailing List
 
 Join us on the "mailing list":http://groups.google.com/group/delayed_job
-
-h2. How to contribute
-
-If you find what looks like a bug:
-
-# Search the "mailing list":http://groups.google.com/group/delayed_job to see if anyone else had the same issue.
-# Check the "GitHub issue tracker":http://github.com/collectiveidea/delayed_job/issues/ to see if anyone else has reported issue.
-# If you don't see anything, create an issue with information on how to reproduce it.
-
-If you want to contribute an enhancement or a fix:
-
-# Fork the project on github.
-# Make your changes with tests.
-# Commit the changes without making changes to the Rakefile or any other files that aren't related to your enhancement or fix
-# Send a pull request.