* Change meta tags to use html entity-escaped text for values, so that

* Change meta tags to use html entity-escaped text for values, so that
  quotes and such can be represented in title tags.
* Depend and build-depend on HTML::Parser for HTML::Entities which is used
  for the above.
* Make --rebuild also cause --aggregate to re-download and write aggregated
  pages.
* Avoid outputting duplicate meta info.
* Include title metadata on aggregated posts for capitalised and un-munged
  titles.