Add a minor fix to the CITATION.rst

Author: drvinceknight

CITATION.rst

@@ -1,7 +1,7 @@
 Please use the following to cite the latest version of the Axelrod library::
 
     @misc{axelrodproject,
-      author       = {{ {The Axelrod project developers} }}
+      author       = {{ {The Axelrod project developers} }},
       title        = {Axelrod: <RELEASE TITLE>},
       month        = apr,
       year         = 2016,