Fix creation of chunk folder if needed.

Use getChunkDirectory instead of getChunksPath to get the path for the
chunks directory.

src/Save/ChunkSave.php

@@ -215,11 +215,11 @@ public function chunkDisk()
      */
     protected function createChunksFolderIfNeeded()
     {
-        $path = $this->getChunksPath();
+        $path = $this->getChunkDirectory();
 
         // creates the chunks dir
         if (!file_exists($path)) {
             mkdir($path, 0777, true);
         }
     }
-}
+}