Detection of invalid sheet name

Based on Excel requirements:
 - it should not be blank
 - it should not exceed 31 characters
 - it should not contain these characters: \ / ? * [ or ]
 - it should be unique

src/Spout/Writer/Exception/InvalidSheetNameException.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Box\Spout\Writer\Exception;
+
+/**
+ * Class InvalidSheetNameException
+ *
+ * @package Box\Spout\Writer\Exception
+ */
+class InvalidSheetNameException extends WriterException
+{
+}