Support cloudsqlpostgres dialect (#1577)
Support cloudsqlpostgres dialect (#1577)

This is needed for proper cloud sql proxy.

see https://github.com/GoogleCloudPlatform/cloudsql-proxy and https://github.com/GoogleCloudPlatform/cloudsql-proxy/blob/master/proxy/dialers/postgres/hook_test.go for details.
jinzhu/gorm,jinzhu/gorm,ModelRocket/gorm,ModelRocket/gorm,ulule/gorm,ulule/gorm