Support for RSS version 0.91

[glacambre]

Checklist

• [x] I checked, but didn't find any duplicates (open OR closed) of this issue in the repo.
• [x] This issue contains only one feature request. I will open one issue for every feature I want to request.

What feature do you want?

I would like News to support RSS version 0.91, so that importing an OPML file containing a feed using this version does not result in a "Unsupported RSS version: 0.91" error message.

Why do you want this feature?

I would like to subscribe to a feed that uses this version: http://tratt.net/laurie/blog/entries.rss . As far as I can tell, version 0.91 and version 2.0, which News supports, seem to be pretty compatible, with version 2.0 just having one less required field.