Itertools are no longer reexported from util, optimized triedb iter

ethcore/src/blockchain/blockchain.rs

@@ -19,6 +19,7 @@
 use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 use std::mem;
+use itertools::Itertools;
 use bloomchain as bc;
 use util::*;
 use rlp::*;