Fixing warnings

ethcore/src/externalities.rs

@@ -301,8 +301,14 @@ mod tests {
 		env_info: EnvInfo
 	}
 
+	impl Default for TestSetup {
+		fn default() -> Self {
+			TestSetup::new()
+		}
+	}
+
 	impl TestSetup {
-		fn new() -> TestSetup {
+		fn new() -> Self {
 			TestSetup {
 				state: get_temp_state(),
 				engine: get_test_spec().to_engine().unwrap(),