Atom feed: support titles with implicit type.

[eostrom]

According to the Atom spec, text constructs such as title may have a type attribute, but if they don't, processors must behave as though it were present with a value of "text".

YQL treats these two cases differently:

"title": {"type": "html", "content": "HTML content"}
"title": "Text content with unspecified type."

With this change, we use the content property if title is an object, and otherwise use title as-is.

[christianvuerings]

@eostrom do you have an example of a feed that breaks? Might be good for reference purposes

[eostrom]

All I have offhand is my brand new blog's feed: http://notebook.erikostrom.com/feed.xml

[christianvuerings]

@eostrom thanks!