Support microtime in returned DateTimeInterface instances

Fixes #90 and supersedes #93.

src/Type/NumberInterface.php

@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * This file is part of the ramsey/uuid library
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @copyright Copyright (c) Ben Ramsey <ben@benramsey.com>
+ * @license http://opensource.org/licenses/MIT MIT
+ */
+
+declare(strict_types=1);
+
+namespace Ramsey\Uuid\Type;
+
+/**
+ * NumberInterface ensures consistency in numeric values returned by ramsey/uuid
+ */
+interface NumberInterface
+{
+    public function toString(): string;
+
+    public function __toString(): string;
+}