only one tableName per query call

lib/query/builder.js

@@ -71,8 +71,7 @@ module.exports = function(client) {
     },
 
     table: function QueryBuilder$table(tableName) {
-      this.statements.push({
-        type: 'table',
+      this._ensureSingle('table', {
         value: this._wrap(tableName)
       });
     },