feature #1 Add an exception for unsupported statement version (Lctrs)

This PR was squashed before being merged into the 0.1.x-dev branch (closes #1).

Discussion
----------

Add an exception for unsupported statement version

Replace php-xapi/serializer#37

Commits
-------

e43c0ac Add an exception for unsupported statement version

Author: xabbuh

CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+0.2.0
+-----
+
+* Added `UnsupportedStatementVersionException`.
+
 0.1.1
 -----
 

src/UnsupportedStatementVersionException.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of the xAPI package.
+ *
+ * (c) Christian Flothmann <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Xabbuh\XApi\Common\Exception;
+
+/**
+ * Unsupported statement version exception.
+ *
+ * @author Jérôme Parmentier <[email protected]>
+ */
+class UnsupportedStatementVersionException extends XApiException
+{
+}