Use correct path in files writer

IPython/nbconvert/writers/files.py

@@ -82,7 +82,7 b' class FilesWriter(WriterBase):'
                     for matching_filename in glob.glob(filename):
 
                         # Make sure folder exists.
-                        dest = os.path.join(self.build_directory, filename)
+                        dest = os.path.join(self.build_directory, matching_filename)
                         path = os.path.dirname(dest)
                         self._makedir(path)