Add adaptor FlatTuples so that izip/iproduct can be Clone
Add adaptor FlatTuples so that izip/iproduct can be Clone

imp/rust-itertools,Wilfred/rust-itertools,DanielKeep/rust-itertools,stepancheg/rust-itertools,flo-l/rust-itertools,tempbottle/rust-itertools,rust-itertools/itertools