Fix Swift add_cell - alive argument should be optional
Fix Swift add_cell - alive argument should be optional

KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations,KieranP/Game-Of-Life-Implementations