Events sub (#126)

* Make event subscription logic more generic.

* Fix build.

* Add test-node.

* Update deps.

* Address review comments.

test-node/src/main.rs

@@ -0,0 +1,28 @@
+// 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
+// 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/>.
+
+//! Substrate Node Template CLI library.
+#![warn(missing_docs)]
+
+mod chain_spec;
+#[macro_use]
+mod service;
+mod cli;
+mod command;
+
+fn main() -> sc_cli::Result<()> {
+    command::run()
+}