Laravel 5.6 updates

Travis config update

Removed HHVM script as Laravel no longer support HHVM after releasing 5.3

vendor/symfony/console/Exception/NamespaceNotFoundException.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Console\Exception;
+
+/**
+ * Represents an incorrect namespace typed in the console.
+ *
+ * @author Pierre du Plessis <pdples@gmail.com>
+ */
+class NamespaceNotFoundException extends CommandNotFoundException
+{
+}