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/values/PhpExtensionRequirementTest.php

@@ -0,0 +1,26 @@
+<?php
+/*
+ * This file is part of PharIo\Manifest.
+ *
+ * (c) Arne Blankerts <arne@blankerts.de>, Sebastian Heuer <sebastian@phpeople.de>, Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace PharIo\Manifest;
+
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers PharIo\Manifest\PhpExtensionRequirement
+ */
+class PhpExtensionRequirementTest extends TestCase {
+    public function testCanBeCreated() {
+        $this->assertInstanceOf(PhpExtensionRequirement::class, new PhpExtensionRequirement('dom'));
+    }
+
+    public function testCanBeUsedAsString() {
+        $this->assertEquals('dom', new PhpExtensionRequirement('dom'));
+    }
+}