Apply fixes from StyleCI (#532)

Author: GrahamCampbell

lib/Gitlab/Api/Version.php

@@ -2,9 +2,9 @@
 
 class Version extends AbstractApi
 {
-	/**
-	 * @return mixed
-	 */
+    /**
+     * @return mixed
+     */
     public function show()
     {
         return $this->get('version');

lib/Gitlab/Exception/MissingArgumentException.php

@@ -9,11 +9,11 @@
  */
 class MissingArgumentException extends ErrorException implements ExceptionInterface
 {
-	/**
-	 * @param string|array $required
-	 * @param int $code
-	 * @param Exception|null $previous
-	 */
+    /**
+     * @param string|array $required
+     * @param int $code
+     * @param Exception|null $previous
+     */
     public function __construct($required, $code = 0, $previous = null)
     {
         if (is_string($required)) {