Add missing license headers and CI check (#98)

* Add missing license headers and add CI check

* Remove log line

* Remove stale todos

src/rpc.rs

@@ -1,4 +1,4 @@
-// Copyright 2019 Parity Technologies (UK) Ltd.
+// Copyright 2019-2020 Parity Technologies (UK) Ltd.
 // This file is part of substrate-subxt.
 //
 // subxt is free software: you can redistribute it and/or modify
@@ -129,8 +129,6 @@ impl<T: System> Rpc<T> {
         key: StorageKey,
         hash: Option<T::Hash>,
     ) -> Result<Option<V>, Error> {
-        // todo: update jsonrpsee::rpc_api! macro to accept shared Client (currently only RawClient)
-        // until then we manually construct params here and in other methods
         let params = Params::Array(vec![to_json_value(key)?, to_json_value(hash)?]);
         let data: Option<StorageData> =
             self.client.request("state_getStorage", params).await?;