Use thiserror instead of derive_more (#44)

- Use thiserror instead of derive_more
- Format code
- Fix clippy warnings
- Add LICENSE_TEMPLATE

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

src/frame/system.rs

@@ -1,17 +1,30 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of substrate-subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with substrate-subxt.  If not, see <http://www.gnu.org/licenses/>.
+
 //! Implements support for the frame_system module.
-use crate::{
-    error::Error,
-    frame::{
-        Call,
-        balances::Balances,
-    },
-    Client,
-};
+
+use std::fmt::Debug;
+
 use futures::future::{
     self,
     Future,
 };
 use parity_scale_codec::Codec;
+use serde::de::DeserializeOwned;
+
 use runtime_primitives::traits::{
     Bounded,
     CheckEqual,
@@ -26,8 +39,15 @@ use runtime_primitives::traits::{
     StaticLookup,
 };
 use runtime_support::Parameter;
-use serde::de::DeserializeOwned;
-use std::fmt::Debug;
+
+use crate::{
+    error::Error,
+    frame::{
+        balances::Balances,
+        Call,
+    },
+    Client,
+};
 
 /// The subset of the `frame::Trait` that a client must implement.
 pub trait System: 'static + Eq + Clone + Debug {