Adds double range use case to README
Adds double range use case to README
ryanhaining/cppitertools,tempbottle/cppitertools,tempbottle/cppitertools,ryanhaining/cppitertools,jkhoogland/cppitertools,jkhoogland/cppitertools,tempbottle/cppitertools,ryanhaining/cppitertools,jkhoogland/cppitertools