add object pool pattern

Tests/Pool/PoolTest.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace DesignPatterns\Tests\Pool;
+
+use DesignPatterns\Pool\Pool;
+
+class TestWorker
+{
+
+    public $id = 1;
+
+}
+
+class PoolTest extends \PHPUnit_Framework_TestCase
+{
+
+    public function testPool()
+    {
+        $pool = new Pool('DesignPatterns\Tests\Pool\TestWorker');
+        $worker = $pool->get();
+
+        $this->assertEquals(1, $worker->id);
+
+        $worker->id = 5;
+        $pool->dispose($worker);
+
+        $this->assertEquals(5, $pool->get()->id);
+        $this->assertEquals(1, $pool->get()->id);
+    }
+
+}
+