• Changed behavior of Entry->summary to prevent it from returning the
  full contents of the entry. Now, in an RSS feed, summary only returns
  a value if there is both a element and one of the
  other elements typically used for the full content.
  
• Changed content model for Entry->content and Entry->summary.
  They now return an XML::Feed::Content object, which knows about both
  the actual content and the MIME type of the content.
  
• Improved feed format detection by first tag in feed.