Added unit test for SSE entity

Author: manpreet.singh

README.md

@@ -1 +1,30 @@
-# apache-sseclient
+# apache-sseclient
+
+This is a wrapper around the Apache HTTP components async client to listen for and process [Server-Sent Events](https://www.w3.org/TR/eventsource/).
+
+### Usage
+
+Create an instance of the async client & start it.
+```
+CloseableHttpAsyncClient asyncClient = HttpAsyncClients.createDefault();
+asyncClient.start();
+```
+
+Create the request.
+```
+SseRequest request = new SseRequest(YOUR_REQUEST_URI);
+```
+
+Create the SSE client instance and provice `ExecutorService` instance to run the requests in a new thread.
+```
+ApacheHttpSseClient sseClient = new ApacheHttpSseClient(asyncClient, Executors.newFixedThreadPool(CONCURRENT_SSE_STREAMS));
+```
+
+Execute the request and get the `Future` response instance.
+```
+Future<SseResponse> sseResponse = sseClient.execute(request);
+```
+
+### Authors
+
+Created by [@ytoh](https://github.com/ytoh) & [@manpreet333](https://github.com/manpreet333) when in the middle of a project we realized Apache client doesn't have this functionality.