This is an attempt to fix#133.
Previously, we just clobbered the recent GUIDs with the lastest response
every single time, assuming that Atom/RSS feeds would consistently return the
same items. This appears to not be the case. In the wild, the number of items
returned on a single request can vary (sometimes even being 1 or 2 when usually
it is 50!).
This patch alters *how many* and *which* GUIDs we keep between requests, in an
attempt to prevent sending old news for buggy RSS feeds.
Kegan Dougal
332b451d77