Modified series4 so that it correctly reversed each element and added a doctring.
Modified series4 so that it correctly reversed each element and added a doctring.

UWPCE-PythonCert/IntroPython2016,weidnem/IntroPython2016,UWPCE-PythonCert/IntroPython2016,Baumelbi/IntroPython2016,UWPCE-PythonCert/IntroPython2016,weidnem/IntroPython2016,weidnem/IntroPython2016,Baumelbi/IntroPython2016