can't parse media:thumbnail

[Gleydson Tavares]

I'm trying to parse an RSS file that has a media thumbnail, but it looks like we don't have support for that yet.

<media:thumbnail url="http://www.foo.com/keyframe.jpg" width="75" height="50" time="12:05:01.123" />

RSS::Parser.parse('https://justthenews.com/syndication/willcountygazette.com/rss.xml')

[Sutou Kouhei]

This can be solved when we solve #18.