rename create client, fix client instance test

src/helpers/es_client.js

@@ -0,0 +1,18 @@
+import elasticsearch from 'elasticsearch';
+
+export default function createClient(options) {
+  let client;
+
+  // if there's a transport property, assume it's a client instance
+  if (isClient(options)) {
+    client = options;
+  } else {
+    client = new elasticsearch.Client(options);
+  }
+
+  return client;
+};
+
+export function isClient(client) {
+  return !!client.transport;
+}