Fix json sql tests
Fix json sql tests

* Make tests deterministic
* Run tests against Postgres

cheungpat/sqlalchemy-utils,konstantinoskostis/sqlalchemy-utils,tonyseek/sqlalchemy-utils,rmoorman/sqlalchemy-utils,tonyseek/sqlalchemy-utils,marrybird/sqlalchemy-utils,JackWink/sqlalchemy-utils,spoqa/sqlalchemy-utils