Add pear modules, mail and net_smtp via composer (#93)

Add pear modules, mail and net_smtp via composer, remove php 5.6 build due to phpunit 6

lib/composer/vendor/phar-io/manifest/tests/xml/ExtElementCollectionTest.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace PharIo\Manifest;
+
+use DOMDocument;
+
+class ExtElementCollectionTest extends \PHPUnit_Framework_TestCase {
+    public function testComponentElementCanBeRetrievedFromCollection() {
+        $dom = new DOMDocument();
+        $dom->loadXML('<?xml version="1.0" ?><ext xmlns="https://phar.io/xml/manifest/1.0" />');
+        $collection = new ExtElementCollection($dom->childNodes);
+
+        foreach($collection as $position => $extElement) {
+            $this->assertInstanceOf(ExtElement::class, $extElement);
+            $this->assertEquals(0, $position);
+        }
+    }
+
+}