Files for the command line now use one letter instead of two, keeping…

… compatibility with previous version of pdftk

src/Shuble/Slurpy/Factory.php

@@ -367,6 +367,6 @@ protected function getPageRange($handle, $input)
      */
     protected function generateFileHandle($index)
     {
-        return chr(65 + floor($index/26) % 26) . chr(65 + $index % 26);
+        return chr(65 + $index % 26);
     }
 }