Merge pull request #722 from souravsingh/fix-links

Fix Link to citations

Author: drvinceknight

docs/citing_the_library.rst

@@ -5,6 +5,6 @@ We would be delighted if anyone wanted to use and/or reference this library for
 their own research.
 
 If you do please let us know and reference the library: as described in the
-`CITATION.txt file on the library
+`CITATION.rst file on the library
 repository
-<https://github.com/Axelrod-Python/Axelrod/blob/master/CITATION.txt>`_.
+<https://github.com/Axelrod-Python/Axelrod/blob/master/CITATION.rst>`_.