Custom stream wrapper support

Added support for custom stream wrappers, such as "fly" or "s3".
Support is determined per reader.

src/Spout/Common/Helper/GlobalFunctionsHelper.php

@@ -280,6 +280,17 @@ class GlobalFunctionsHelper
         return mb_convert_encoding($string, $targetEncoding, $sourceEncoding);
     }
 
+    /**
+     * Wrapper around global function stream_get_wrappers()
+     * @see stream_get_wrappers()
+     *
+     * @return array
+     */
+    public function stream_get_wrappers()
+    {
+        return stream_get_wrappers();
+    }
+
     /**
      * Wrapper around global function stream_get_line()
      * @see stream_get_line()