Using findCreateFind instead of using findOrCreate

 `findOrCreate` does the select and insert (if necessary) in a transaction.
 For the purpose of sequelize store set, this is probably not required as
 updating the same session concurrently in more than one request might not be
 applicable.
 Using `findOrCreate` has shown a high memory usage and potentially crashing the DB
 under postgres, as sequelize uses temp functions setup transactions and trace any
 failures.
 This change is to use the more performant non-transactional `findCreateFind` function.

lib/connect-session-sequelize.js

@@ -84,7 +84,7 @@ module.exports = function SequelizeSessionInit (Store) {
       defaults = this.options.extendDefaultFields(defaults, data)
     }
 
-    return this.sessionModel.findOrCreate({where: {'sid': sid}, defaults: defaults}).spread(function sessionCreated (session) {
+    return this.sessionModel.findCreateFind({where: {'sid': sid}, defaults: defaults}).spread(function sessionCreated (session) {
       var changed = false
       Object.keys(defaults).forEach(function (key) {
         if (key === 'data') {