Use 'host' instead of 'hostname' for PostgreSQL database settings.

setup.rb configures PG w/ 'hostname' when it should use 'host'

See dbconsole:
https://github.com/rails/rails/blob/3-2-stable/railties/lib/rails/commands/dbconsole.rb#L85

See postgresql_adapter:
https://github.com/rails/rails/blob/3-2-stable/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb#L15