firefox: update copyright

helpers/make-firefox

 #!/bin/bash
 #
 #    Copyright (C) 2008-2014  Ruben Rodriguez <ruben@trisquel.info>
+#    Copyright (C) 2015       Santiago Rodriguez <santi@trisquel.info>
 #
 #    This program is free software; you can redistribute it and/or modify
 #    it under the terms of the GNU General Public License as published by