Linked contribution information in README

For potential contributors who are new to GitHub and prefer to learn via structured processes, linking the Contributor's Guide and development philosophy documents in the README will make it easier for them to find this information. This will increase the quality of their contributions and make them more comfortable contributing to the project.

Author: zurbrugc

README.md

@@ -89,17 +89,18 @@ Fantastic documentation is available at
 How to Contribute
 -----------------
 
-1.  Check for open issues or open a fresh issue to start a discussion
+1.  Become more familiar with the project by reading our [Contributor's Guide](http://docs.python-requests.org/en/latest/dev/contributing/) and our [development philosophy](http://docs.python-requests.org/en/latest/dev/philosophy/).
+2.  Check for open issues or open a fresh issue to start a discussion
     around a feature idea or a bug. There is a [Contributor
     Friendly](https://github.com/requests/requests/issues?direction=desc&labels=Contributor+Friendly&page=1&sort=updated&state=open)
     tag for issues that should be ideal for people who are not very
     familiar with the codebase yet.
-2.  Fork [the repository](https://github.com/requests/requests) on
+3.  Fork [the repository](https://github.com/requests/requests) on
     GitHub to start making your changes to the **master** branch (or
     branch off of it).
-3.  Write a test which shows that the bug was fixed or that the feature
+4.  Write a test which shows that the bug was fixed or that the feature
     works as expected.
-4.  Send a pull request and bug the maintainer until it gets merged and
+5.  Send a pull request and bug the maintainer until it gets merged and
     published. :) Make sure to add yourself to
     [AUTHORS](https://github.com/requests/requests/blob/master/AUTHORS.rst).