Add PostgreSQL query generation
Remove SQL injection vector from strings
Add preliminary Postgres DB stuff
Add Postgres adapter to perpetuity.rb
Allow specs to be run with Postgres adapter
Add id column generation, object counts, etc
Require attrs to insert with data_source adapters
Return 0 for count for nonexistent tables
Add deletion and better Postgres serialization
Defer to spec_helper to configure DB for indexes
Remove DB-specific code

MongoDB and Postgres adapters have been moved to their own gems.
Set up dependencies properly