output: Add URL and timestamp of crawling, to footer

This should make it a bit easier to track down the author for more
interesting work.

Signed-off-by: Carl Helmertz <helmertz@gmail.com>
stdout: Be silent when you should

The 'recommended' bash alias for save, dumped the whole markdown into
the terminal.

Signed-off-by: Carl Helmertz <helmertz@gmail.com>