I feel like it would make more sense to have ```schema_loaded?(dbname, file)```.  And instead of using the schema filename (either ```tmp/rails_parallel/schema/*.sql``` or ```db/shard-whatever.sql```, we could perhaps read and hash the SQL file and put that in the ```schema_migrations``` table instead.

In fact, maybe it should calculate the hash of the file in ```schema_load``` and ```return if schema_loaded?(name, hash)```, then put the hash into ```schema_migrations``` at the end.