Add option to dump schema without owner

[jayrosen1576]

We are using soda in an automated deployment scenario and we are running into issues with the schema that is output after a migrate up. Currently there is no way to prevent the owner of tables from being dumped to the schema.sql file, and we may have deployments where the owner varies per instance. It would be great if there was a way to extent the below function to include other postgresql pg_dump options:

func (p *postgresql) DumpSchema(w io.Writer) error {
	cmd := exec.Command("pg_dump", "-s", fmt.Sprintf("--dbname=%s", p.URL()))
	return genericDumpSchema(p.Details(), cmd, w)
}

[paxer]

As a workaround, we've added migrations/schema.sql to .gitignore, and on CI we always force migrations to run instead of loading from the schema.sql e.g.

buffalo test --force-migrations