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

… integration

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

CONTRIBUTING.md

@@ -0,0 +1,49 @@
+## Contributing
+In the spirit of [free software][free-sw], **everyone** is encouraged to help
+improve this project.
+
+[free-sw]: http://www.fsf.org/licensing/essays/free-sw.html
+
+Here are some ways *you* can contribute:
+
+* by using alpha, beta, and prerelease versions
+* by reporting bugs
+* by suggesting new features
+* by writing or editing documentation
+* by writing specifications
+* by writing code (**no patch is too small**: fix typos, add comments, clean up
+inconsistent whitespace)
+* by refactoring code
+* by fixing [issues][]
+* by reviewing patches
+
+[issues]: https://github.com/sferik/twitter/issues
+
+## Submitting an Issue
+We use the [GitHub issue tracker][issues] to track bugs and features. Before
+submitting a bug report or feature request, check to make sure it hasn't
+already been submitted. When submitting a bug report, please include a [Gist][]
+that includes a stack trace and any details that may be necessary to reproduce
+the bug, including your gem version, Ruby version, and operating system.
+Ideally, a bug report should include a pull request with failing specs.
+
+[gist]: https://gist.github.com/
+
+## Submitting a Pull Request
+1. [Fork the repository.][fork]
+2. [Create a topic branch.][branch]
+3. Add specs for your unimplemented feature or bug fix.
+4. Run `bundle exec rake spec`. If your specs pass, return to step 3.
+5. Implement your feature or bug fix.
+6. Run `bundle exec rake spec`. If your specs fail, return to step 5.
+7. Run `open coverage/index.html`. If your changes are not completely covered
+   by your tests, return to step 3.
+8. Add documentation for your feature or bug fix.
+9. Run `bundle exec rake yard`. If your changes are not 100% documented, go
+   back to step 8.
+10. Add, commit, and push your changes.
+11. [Submit a pull request.][pr]
+
+[fork]: http://help.github.com/fork-a-repo/
+[branch]: http://learn.github.com/p/branching.html
+[pr]: http://help.github.com/send-pull-requests/

README.md

@@ -369,56 +369,6 @@ Here are some fun facts about this library:
 
 [stats]: https://rubygems.org/gems/twitter
 
-## Contributing
-In the spirit of [free software][free-sw], **everyone** is encouraged to help
-improve this project.
-
-[free-sw]: http://www.fsf.org/licensing/essays/free-sw.html
-
-Here are some ways *you* can contribute:
-
-* by using alpha, beta, and prerelease versions
-* by reporting bugs
-* by suggesting new features
-* by writing or editing documentation
-* by writing specifications
-* by writing code (**no patch is too small**: fix typos, add comments, clean up
-  inconsistent whitespace)
-* by refactoring code
-* by fixing [issues][]
-* by reviewing patches
-
-[issues]: https://github.com/sferik/twitter/issues
-
-## Submitting an Issue
-We use the [GitHub issue tracker][issues] to track bugs and features. Before
-submitting a bug report or feature request, check to make sure it hasn't
-already been submitted. When submitting a bug report, please include a [Gist][]
-that includes a stack trace and any details that may be necessary to reproduce
-the bug, including your gem version, Ruby version, and operating system.
-Ideally, a bug report should include a pull request with failing specs.
-
-[gist]: https://gist.github.com/
-
-## Submitting a Pull Request
-1. [Fork the repository.][fork]
-2. [Create a topic branch.][branch]
-3. Add specs for your unimplemented feature or bug fix.
-4. Run `bundle exec rake spec`. If your specs pass, return to step 3.
-5. Implement your feature or bug fix.
-6. Run `bundle exec rake spec`. If your specs fail, return to step 5.
-7. Run `open coverage/index.html`. If your changes are not completely covered
-   by your tests, return to step 3.
-8. Add documentation for your feature or bug fix.
-9. Run `bundle exec rake yard`. If your changes are not 100% documented, go
-   back to step 8.
-10. Add, commit, and push your changes.
-11. [Submit a pull request.][pr]
-
-[fork]: http://help.github.com/fork-a-repo/
-[branch]: http://learn.github.com/p/branching.html
-[pr]: http://help.github.com/send-pull-requests/
-
 ## Supported Ruby Versions
 This library aims to support and is [tested against][travis] the following Ruby
 version: