Added an handler for NewRelic:

* implemented a test which verifies that the fallback handler handles records when the NewRelic PHP extension is not installes
* implemented the actual handler

tests/Monolog/Handler/NewRelicHandlerTest.php

@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * This file is part of the Monolog package.
+ *
+ * (c) Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Monolog\Handler;
+
+use Monolog\TestCase;
+use Monolog\Logger;
+
+class NewRelicHandlerTest extends TestCase
+{
+    public function testFallbackHandler()
+    {
+        $handler         = new NewRelicHandler();
+        $fallbackHandler = new TestHandler();
+        $handler->setFallbackHandler($fallbackHandler);
+        $record          = array(
+            'level' => Logger::DEBUG,
+            'extra' => array(),
+        );
+        
+        $handler->handle($record);
+        
+        $this->assertCount(1, $fallbackHandler->getRecords());
+    }
+}