Not going to have LocalArchive anymore

I don't think there's any real-world use for it, and I'd rather put
everything through one class, just fake out the S3 part for testing.
For now, I'm okay actually using S3, I'll put in the faking when I
need to be working offline.
Oh, Amazon has an official SDK. use that.
breaking apart archived items and metadata
split items up into bins when storing them
split up archived feeds into bins
proper handling for requesting items off the end of the archive
Change feed.rb so that it's always archive-backed
Trickle changes down to rerun, make tests pass
Trickling archiving changes up to the webapp

I've also added caching of some objects in feed.rb and fetch.rb. This
has brought execution time (locally) of a preview page down from 25-30s
to 6s for theamphour.com/feed
change some copy to reflect archiving everything
Merge branch 'archiving'
removing cruft
Abstracted away s3 storage so that we can at least in theory use local storage, or whatever else
at first glance, things seem to be working
Merge branch 'storeshim'
Taking care of bugs in the DiskStore
Automating some work with rake
Tests can be run against s3 or not
instead of whitelisting, just check if we've cached the feed
oh man I think things mostly work

- don't change dates (re-broadcast) when it's really a pass-through
- work sensibly with feeds that are caught up