added percentiles aggregation

src/Aggregation/Pipeline/PercentilesBucketAggregation.php

+<?php
+
+/*
+ * This file is part of the ONGR package.
+ *
+ * (c) NFQ Technologies UAB <info@nfq.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace ONGR\ElasticsearchDSL\Aggregation\Pipeline;
+
+/**
+ * Class representing Percentiles Bucket Pipeline Aggregation.
+ *
+ * @link https://goo.gl/bqi7m5
+ */
+class PercentilesBucketAggregation extends AbstractPipelineAggregation
+{
+    /**
+     * @var array
+     */
+    private $percents;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getType()
+    {
+        return 'percentiles_bucket';
+    }
+
+    /**
+     * @return array
+     */
+    public function getPercents()
+    {
+        return $this->percents;
+    }
+
+    /**
+     * @param array $percents
+     */
+    public function setPercents(array $percents)
+    {
+        $this->percents = $percents;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getArray()
+    {
+        $data = ['buckets_path' => $this->getBucketsPath()];
+
+        if ($this->getPercents()) {
+            $data['percents'] = $this->getPercents();
+        }
+
+        return $data;
+    }
+}