Added support for cluster stats

Elasticsearch v0.90.8
See elastic/elasticsearch@2b6214c

src/main/scala/scalastic/elasticsearch/ClusterAdmin.scala

@@ -1,6 +1,10 @@
 package scalastic.elasticsearch
 
-trait ClusterAdmin extends Health with Nodes with State with Metadata {
+trait ClusterAdmin extends Health
+  with Nodes
+  with State
+  with Metadata
+  with ClusterStats {
   self: Indexer =>
 }
 
@@ -98,3 +102,11 @@ trait Metadata {
   def metadataFor(index: String, `type`: String) = metadata.index(index).mappings.get(`type`)
   def fieldsOf(index: String, `type`: String) = metadataFor(index, `type`).sourceAsMap.get("properties").asInstanceOf[Map[String, Object]]
 }
+
+trait ClusterStats {
+  self: Indexer =>
+
+  def clusterStats() = clusterStats_send().actionGet
+  def clusterStats_send() = clusterStats_prepare().execute
+  def clusterStats_prepare() = client.admin.cluster.prepareClusterStats
+}