fix: Partial files are not added

By mistake, we use (django_partial) and (djangojs_partial) naming
instead of (django-partial.po) and (djangojs-partial.po)

This is considered a patch to #129

i18n/extract.py

@@ -171,7 +171,7 @@ def run(self, args):
         files_to_clean.update(segmented_files)
 
         # Add partial files to the list of files to clean.
-        files_to_clean.update(('django_partial', 'djangojs_partial'))
+        files_to_clean.update(('django-partial.po', 'djangojs-partial.po'))
 
         # Finish each file.
         for filename in files_to_clean: