In order to help remember the stories of those who were touched by the 2013 Boston Marathon attacks, the Boston Theater Company is staging a documentary play, “Finish Line: The Untold Stories of the 2013 Boston Marathon.” The play tells the stories of 33 survivors, first responders and others affected by the bombings, using nothing but their own words. BU News Service’s Jonathan Gang spoke with co-creators Joey Frangieh and Lisa Rafferty to find out more.