Update coding style to include PSR-12, among other options

This also includes heavy use of slevomat/coding-standard to apply
various checks to the code, based on maintainer (me) preference.

src/BinaryUtils.php

@@ -1,5 +1,17 @@
 <?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;
 
 /**
@@ -10,13 +22,16 @@ class BinaryUtils
     /**
      * Applies the RFC 4122 variant field to the `clock_seq_hi_and_reserved` field
      *
-     * @param int $clockSeqHi
+     * @link http://tools.ietf.org/html/rfc4122#section-4.1.1 RFC 4122, § 4.1.1: Variant
+     *
+     * @param int $clockSeqHi The value of `clock_seq_hi_and_reserved` field
+     *     before the RFC 4122 variant is applied
+     *
      * @return int The high field of the clock sequence multiplexed with the variant
-     * @link http://tools.ietf.org/html/rfc4122#section-4.1.1
      */
-    public static function applyVariant($clockSeqHi): int
+    public static function applyVariant(int $clockSeqHi): int
     {
-        // Set the variant to RFC 4122
+        // Set the variant to RFC 4122.
         $clockSeqHi = $clockSeqHi & 0x3f;
         $clockSeqHi |= 0x80;
 
@@ -26,10 +41,13 @@ class BinaryUtils
     /**
      * Applies the RFC 4122 version number to the `time_hi_and_version` field
      *
-     * @param string $timeHi
-     * @param int $version
+     * @link http://tools.ietf.org/html/rfc4122#section-4.1.3 RFC 4122, § 4.1.3: Version
+     *
+     * @param string $timeHi The value of the `time_hi_and_version` field before
+     *     the RFC 4122 version is applied
+     * @param int $version The RFC 4122 version to apply to the `time_hi` field
+     *
      * @return int The high field of the timestamp multiplexed with the version number
-     * @link http://tools.ietf.org/html/rfc4122#section-4.1.3
      */
     public static function applyVersion(string $timeHi, int $version): int
     {