replaces testgroupby with groupby examples
replaces testgroupby with groupby examples

jkhoogland/cppitertools,tempbottle/cppitertools,tempbottle/cppitertools,jkhoogland/cppitertools,ryanhaining/cppitertools,ryanhaining/cppitertools,tempbottle/cppitertools,jkhoogland/cppitertools,ryanhaining/cppitertools