fixed: DML if object value is null, JSON.stringify return string 'null'
Add initial postgres driver tests
Merge pull request #426 from dresende/pr/380

Pr/380
Convert tabs -> spaces in example to make it easier to read on github
Update to new sql-ddl-sync
Remove unstable tests
Merge pull request #433 from dresende/key

Update to new sql-ddl-sync
Merge remote-tracking branch 'orm2/master'