Remove "rails3" naming left over from old days of Rails 2.x support
Rename Octopus::Association -> Octopus::AssociationShardTracking
Rename Octopus::AssociationCollection -> Octopus::CollectionAssociation
Use Octopus::ShardTracking::* modules to factor out shard-tracking behavior
Add shard tracking support to CollectionProxy
Add Octopus::RelationProxy for shard-friendly (delayed) evaluation of ActiveRecord::Relation objects