tests takewhile when first element fails predicate
tests takewhile when first element fails predicate

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