Revert "Removing old documentation mentioning NodeBuilder."

This reverts commit 3ca02d647e.

docs/groovy-api/client.asciidoc

@@ -0,0 +1,59 @@
+[[client]]
+== Client
+
+Obtaining an elasticsearch Groovy `GClient` (a `GClient` is a simple
+wrapper on top of the Java `Client`) is simple. The most common way to
+get a client is by starting an embedded `Node` which acts as a node
+within the cluster.
+
+
+[[node-client]]
+=== Node Client
+
+A Node based client is the simplest form to get a `GClient` to start
+executing operations against elasticsearch.
+
+[source,js]
+--------------------------------------------------
+import org.elasticsearch.groovy.client.GClient
+import org.elasticsearch.groovy.node.GNode
+import static org.elasticsearch.groovy.node.GNodeBuilder.nodeBuilder
+
+// on startup
+
+GNode node = nodeBuilder().node();
+GClient client = node.client();
+
+// on shutdown
+
+node.close();
+--------------------------------------------------
+
+Since elasticsearch allows to configure it using JSON based settings,
+the configuration itself can be done using a closure that represent the
+JSON:
+
+[source,js]
+--------------------------------------------------
+import org.elasticsearch.groovy.node.GNode
+import org.elasticsearch.groovy.node.GNodeBuilder
+import static org.elasticsearch.groovy.node.GNodeBuilder.*
+
+// on startup
+
+GNodeBuilder nodeBuilder = nodeBuilder();
+nodeBuilder.settings {
+    node {
+        client = true
+    }
+    cluster {
+        name = "test"
+    }
+}
+
+GNode node = nodeBuilder.node()
+
+// on shutdown
+
+node.stop().close()
+--------------------------------------------------