Made a pretty formatting of the CONTRIBUTING file.

docs/CONTRIBUTING.txt → docs/CONTRIBUTING.rst

@@ -2,10 +2,12 @@ Welcome, and thank you for your interest in contributing!
 =========================================================
 
 If you are looking for a good way to contribute to the Cython project, please
-- have a look at the [Cython Hacker Guide](https://github.com/cython/cython/wiki/HackerGuide)
-- look through the [issues that need help](https://github.com/cython/cython/issues?q=is%3Aissue+is%3Aopen+view+label%3A%22help+wanted%22)
-- look through the [issues that are a good entry point for beginners](https://github.com/cython/cython/issues?q=is%3Aissue+is%3Aopen+view+label%3A%22good+first+issue%22)
+
+* have a look at the `Cython Hacker Guide <https://github.com/cython/cython/wiki/HackerGuide>`_.
+* look through the `issues that need help <https://github.com/cython/cython/issues?q=is%3Aissue+is%3Aopen+view+label%3A%22help+wanted%22>`_.
+* look through the `issues that are a good entry point for beginners <https://github.com/cython/cython/issues?q=is%3Aissue+is%3Aopen+view+label%3A%22good+first+issue%22>`_
 
 If you have code that you want to contribute, please make sure that it
-- includes tests in the `tests/` directory (see the [Hacker Guide on Testing](https://github.com/cython/cython/wiki/HackerGuide#the-test-suite))
-- comes in form of a pull request
+
+* includes tests in the `tests/` directory (see the `Hacker Guide on Testing <https://github.com/cython/cython/wiki/HackerGuide#the-test-suite>`_)
+* comes in form of a pull request