dumper: Change gap between missing ticks to 60 seconds to reduce server load.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
dumper: Add useragent to avoid 403 errors from CloudFlare's "Browser Integrity Check".

NOTE: If you are using this script, please add your IRC nick as indicated so that an admin can contact you if there is a problem.

Signed-off-by: Martin Stone <martin@d7415.co.uk>