Fix Simplenote breaking change (#83)

Fixes some export expectations.

Author: beaucollins

src/simperium/client.js

@@ -301,3 +301,6 @@ function defaultWebsocketClientProvider( url ) {
 	}
 	return new WebSocketClient( url );
 }
+
+// Simplenote expects this.
+Client.Bucket = Bucket;

test/simperium/client_test.js

@@ -1,4 +1,4 @@
-import { Client } from '../../src/simperium/client';
+import Client from '../../src/simperium/client';
 import * as events from 'events';
 import { equal, ok } from 'assert';