separate trie from util and make its dependencies into libs:

* bytes
* hashdb
* memorydb
* nibbleslice
* nibblevec

ethcore/src/client/test_client.rs

@@ -27,6 +27,7 @@ use bigint::prelude::U256;
 use bigint::hash::H256;
 use parking_lot::RwLock;
 use util::*;
+use bytes::Bytes;
 use rlp::*;
 use ethkey::{Generator, Random};
 use devtools::*;