swanson/stringer — pull request #238 by Koronen (2013-07-22 09:13:48+00:00)
Title: Use .opml as file extension when exporting OPML

I would argue that it's better to use the more specific `.opml` file extension over just `.xml` when exporting feeds as OPML. I believe this is the same behavior as was found in `BIG_FREE_READER`.