Add pubsub interface definition (#54)

* Add pubsub interface definition

* Functional JsonRpcCoder

* Functional HttpProvider

* Functional WsProvider

* Functional split completed

* Split actual method subscription

* Update flow

* Flatten no user-specified array in sub call

packages/api-provider/src/coder/json/encodeJson.spec.js

@@ -0,0 +1,19 @@
+// Copyright 2017-2018 Jaco Greeff
+// This software may be modified and distributed under the terms
+// of the ISC license. See the LICENSE file for details.
+
+const createCoder = require('./index');
+
+describe('encodeJson', () => {
+  let coder;
+
+  beforeEach(() => {
+    coder = createCoder();
+  });
+
+  it('encodes a valid JsonRPC JSON string', () => {
+    expect(
+      coder.encodeJson('method', 'params')
+    ).toEqual('{"id":1,"jsonrpc":"2.0","method":"method","params":"params"}');
+  });
+});