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/sebastian/diff/tests/TimeEfficientImplementationTest.php

@@ -0,0 +1,22 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of sebastian/diff.
+ *
+ * (c) 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 SebastianBergmann\Diff;
+
+/**
+ * @covers SebastianBergmann\Diff\TimeEfficientLongestCommonSubsequenceCalculator
+ */
+final class TimeEfficientImplementationTest extends LongestCommonSubsequenceTest
+{
+    protected function createImplementation()
+    {
+        return new TimeEfficientLongestCommonSubsequenceCalculator;
+    }
+}