Fix travis error of postgres.
Created by: hiroponz
It referred to http://stackoverflow.com/questions/14265983/upgrading-capybara-from-1-0-1-to-1-1-4-makes-database-cleaner-break-my-specs.
Created by: hiroponz
It referred to http://stackoverflow.com/questions/14265983/upgrading-capybara-from-1-0-1-to-1-1-4-makes-database-cleaner-break-my-specs.