Moves Contributing Guidelines to CONTRIBUTING file

Following Github conventions:
https://github.com/blog/1184-contributing-guidelines

CONTRIBUTING.md

@@ -0,0 +1,20 @@
+We :heart: pull requests. Here's a quick guide:
+
+## Contributing
+
+1. Fork it
+2. Run the tests and make sure they pass :thumbsup: (`bundle && rake`)
+3. Add a test for your change
+4. Make the test pass
+5. Submit a pull request:
+    * Create your feature branch (`git checkout -b my-new-feature`)
+    * Commit your changes (`git commit -am 'Add some feature'`)
+    * Push to the branch (`git push origin my-new-feature`)
+    * Create new Pull Request
+
+## Guidelines
+
+* Include tests that fail without your code, but pass with your code
+* Follow coding conventions found in the current project
+* Update the documentation, examples, and/or anything that is
+affected by your contribution

README.md

@@ -180,10 +180,3 @@ and blue during a break e.g.
 
 ![tmux status bar](http://i.imgur.com/uIzM3.png)
 
-## Contributing
-
-1. Fork it
-2. Create your feature branch (`git checkout -b my-new-feature`)
-3. Commit your changes (`git commit -am 'Add some feature'`)
-4. Push to the branch (`git push origin my-new-feature`)
-5. Create new Pull Request