Laravel 5.6 updates

Travis config update

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

vendor/phpunit/php-timer/src/Exception.php

@@ -0,0 +1,15 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of phpunit/php-timer.
+ *
+ * (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\Timer;
+
+interface Exception
+{
+}