Don't return an error if a user is not yet in the datastore.
Add webfeed: a new syndication feed reader.

This isn't hooked in yet, but you can run go run main.go in the feedz
directory to try it out on a couple feeds.
Use the new RSS and Atom feed reader.

Fixes #40
Report which feed had an error when uploading an OPML.
Improved time parsing.

Try parsing times in more formats, and do not make time errors fatal.
Return the zero time and log the unparsable string.
If a feed or article title is empty, use the URL.

For articles, I we first try the summary then fallback on the URL.

Fixes #70
Handle CDATA in <content:encoding>.

Fixes #57
Don't use innerxml for Atom contents entries, just get the bytes.