Add Justin Duke to the CONTRIBUTORS file
Add Justin Duke to the CONTRIBUTORS file

CivicVision/datahub,USStateDept/FPA_Core,CivicVision/datahub,pudo/spendb,USStateDept/FPA_Core,openspending/spendb,nathanhilbert/FPA_Core,USStateDept/FPA_Core,pudo/spendb,openspending/spendb,spendb/spendb,nathanhilbert/FPA_Core,nathanhilbert/FPA_Core,CivicVision/datahub,spendb/spendb,johnjohndoe/spendb,spendb/spendb,johnjohndoe/spendb,openspending/spendb,johnjohndoe/spendb,pudo/spendb