Add cluster feature docs

Author: nicktorwald

README.md

@@ -213,13 +213,20 @@ tarantool> function getClusterNodes() return { 'host1', 'host2', 'host3' } end
 TarantoolClusterClientConfig config = new TarantoolClusterClientConfig();
 // fill other settings
 config.clusterDiscoveryEntryInstance = "10.0.0.15:3301";        // target discovery server
-config.clusterDiscoveryEntryFunction = "myDiscoveryFunction";   // discovery function used to fetch nodes 
+config.clusterDiscoveryEntryFunction = "getClusterNodes";   // discovery function used to fetch nodes 
 config.clusterDiscoveryDelayMillis = 60_000; // how often client polls the discovery server  
 ```
 
 See [TarantoolClientConfig](http://tarantool.github.io/tarantool-java/apidocs/index.html?org/tarantool/TarantoolClientConfig.html)
 javadoc for more information.
 
+3. Create a client using the config made above.
+
+```java
+TarantoolClusterClient client = new TarantoolClusterClient(config);
+client.syncOps().insert(45, Arrays.asList(1, 1));
+```
+
 #### Auto-discovery caveats
 
 * You need to supply both `clusterDiscoveryEntryInstance` and `clusterDiscoveryEntryFunction`