Distinguish item newness only by URL

Schneier on Security changes update time whenever a comment is posted
AnandTech changes the body of an item with some sort of tracking link

It seems the only thing that will not cause a flood of falsely updated
items is only looking at the URL
Bump version to 0.4.0
Fetch feeds in parallel

fixes #2
Increase pgx MsgBufSize to reduce reallocs
Bump version to 0.4.1