[FIX] Allow uploading media with special chars

The file system does not know about UTF-8 encoded files. Fix #90.

Author: mynetx

src/codebird.php

@@ -1091,18 +1091,20 @@ protected function _buildMultipart($method, $params)
 
             // check for filenames
             if (in_array($key, $possible_files)) {
+                // the file system does not know about UTF-8 filenames
+                $filename_decoded = utf8_decode($value);
                 if (// is it a file, a readable one?
-                    @file_exists($value)
-                    && @is_readable($value)
+                    @file_exists($filename_decoded)
+                    && @is_readable($filename_decoded)
 
                     // is it a valid image?
-                    && $data = @getimagesize($value)
+                    && $data = @getimagesize($filename_decoded)
                 ) {
                     // is it a supported image format?
                     if (in_array($data[2], $this->_supported_media_files)) {
                         // try to read the file
                         ob_start();
-                        readfile($value);
+                        readfile($filename_decoded);
                         $data = ob_get_contents();
                         ob_end_clean();
                         if (strlen($data) === 0) {