plparse: Add image URLs from RSS feeds
plparse: Add image URLs from RSS feeds

Will give us thumbnails for:
http://www.theguardian.com/video/rss

MathieuDuponchelle/totem-pl-parser,MathieuDuponchelle/totem-pl-parser,pwithnall/totem-pl-parser,pwithnall/totem-pl-parser,MathieuDuponchelle/totem-pl-parser,MathieuDuponchelle/totem-pl-parser