Bring back default filename_pattern so that by default we run all galleries.

Signed-off-by: Edward Z. Yang <ezyang@fb.com>

Author: ezyang

conf.py

@@ -65,6 +65,7 @@
     'examples_dirs': ['beginner_source', 'intermediate_source',
                       'advanced_source', 'recipes_source'],
     'gallery_dirs': ['beginner', 'intermediate', 'advanced', 'recipes'],
+    'filename_pattern': 'tutorial.py',
     'backreferences_dir': False
 }