Fixing some clippy warnings

ethcore/src/state/account.rs

@@ -449,7 +449,6 @@ mod tests {
 	use util::*;
 	use super::*;
 	use account_db::*;
-	use rlp::*;
 
 	#[test]
 	fn account_compress() {

ethcore/src/state/mod.rs

@@ -445,6 +445,7 @@ impl State {
 	}
 
 	/// Add `incr` to the balance of account `a`.
+	#[cfg_attr(feature="dev", allow(single_match))]
 	pub fn add_balance(&mut self, a: &Address, incr: &U256, cleanup_mode: CleanupMode) {
 		trace!(target: "state", "add_balance({}, {}): {}", a, incr, self.balance(a));
 		let is_value_transfer = !incr.is_zero();

ethcore/src/state/substate.rs

@@ -57,6 +57,7 @@ impl Substate {
 	}
 
 	/// Get the cleanup mode object from this.
+	#[cfg_attr(feature="dev", allow(wrong_self_convention))]
 	pub fn to_cleanup_mode(&mut self, schedule: &Schedule) -> CleanupMode {
 		match (schedule.no_empty, schedule.kill_empty) {
 			(false, _) => CleanupMode::ForceCreate,