Unify item parsing.
Use update timestamp if publication timestamp is missing.
Add RFC 822 date parsing.
Open https urls with the https class.

It seems that opening a url while specifying a class that is
different from the url's schema results in downloading the url
and opening a local file. We still don't want to use a normal
shell-exec function on untrusted data, so change the class in this
case.
Fix <link> hack to work with <!CDATA[[...]]>
Read encoding from content type.
Tweak RFC 822 timestamp parsing.

Use EDT vs EST to disambiguate local timestamps that would otherwise
be amgibuous, and fix the military timezones.
Show tooltips in item list.
Don't store summaries in tags.
Cut off invalid items from end of tags.