added staging env to cluster.js
added staging env to cluster.js

calvinmetcalf/CartoDB-SQL-API,calvinmetcalf/CartoDB-SQL-API,calvinmetcalf/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,calvinmetcalf/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API,CartoDB/CartoDB-SQL-API,CartoDB/CartoDB-SQL-API,dbirchak/CartoDB-SQL-API