Adds contribution guidelines to the README

README.md

@@ -1,4 +1,32 @@
 # [httpstatus.es](http://httpstatus.es)
 
 [httpstatus.es](http://httpstatus.es) is an easy to reference database of HTTP Status Codes
-with their definitions and helpful code references.
+with their definitions and helpful code references.
+
+## Contributing
+
+All contributions are welcome! If you have an idea to improve the website please
+submit a pull request or [create an issue][1], or provide your thoughts on any
+[open issues][1].
+
+Each status code lives in a Markdown file at [contents/codes](contents/codes),
+the easiest way to submit changes is via the GitHub editor. When contributing
+changes to the status codes please be mindful of the following:
+
+* Soft line length of 80 for Markdown
+* Markdown links should be used as [references instead of inline][2]
+* If an RFC or external document is referenced, make the reference a link
+* Source information on a status code from the most recent standards available
+    (Status Code standards directory is available on [iana.org][3])
+* The opening paragraph of a status code should describe the meaning, following
+    paragraphs can describe implementation
+* Don't edit the meaning of descriptions, but formatting and structural
+    changes are a-okay
+* [Don't double-space after a period][4], and remove any examples of it
+* If the description references a section in the current RFC, always add the RFC
+    identifier. For example "Section 6.6" should become "RFC1234 Section 6.6"
+
+[1]: <https://github.com/citricsquid/httpstatus.es/issues>
+[2]: <https://daringfireball.net/projects/markdown/syntax#link>
+[3]: <http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml>
+[4]: <http://www.slate.com/articles/technology/technology/2011/01/space_invaders.html>