Overhaulin'

1. Changed some local tables to ngx.shared.DICTs in order to let
multiple workers behave. Additional nginx.conf now required.
2. Quicksort was broken. Replaced it with table.sort.
3. Buckets per upstream should stay same, otherwise loss of any upstream
causes a lot more of the keys to be moved. It is hardcoded as
MMC_CONSISTENT_BUCKETS / 10.
4. Defined remove_upstream method to signal lost upstream servers.
5. Lazy init is not preferable. Moved to add/remove upstream.
6. Add/remove upstream should not re-init if upstream set does not change
7. Weighing upstreams removed
Added nginx conf doc