Allow filtering of directories

Fixes prompt-toolkit#294

Author: tony

prompt_toolkit/contrib/completers/filesystem.py

@@ -80,9 +80,11 @@ def get_completions(self, document, complete_event):
                     # (We don't add them to the `completion`. Users can type it
                     # to trigger the autocompletion themself.)
                     filename += '/'
-                else:
-                    if self.only_directories or not self.file_filter(full_name):
-                        continue
+                elif self.only_directories:
+                    continue
+
+                if not self.file_filter(full_name):
+                    continue
 
                 yield Completion(completion, 0, display=filename)
         except OSError: