start a transaction when calling sequelize.transaction

lib/sequelize.js

@@ -390,10 +390,16 @@ module.exports = (function() {
   Sequelize.prototype.transaction = function(_options, _callback) {
     var options     = (typeof _options === 'function') ? {} : _options
       , callback    = (typeof _options === 'function') ? _options : _callback
-      , transaction = new Transaction(options)
+      , transaction = new Transaction(this, options)
+      , self        = this
 
     Utils.tick(function() {
-      callback(transaction)
+      self
+        .getQueryInterface()
+        .startTransaction({ transaction: transaction })
+        .success(function() {
+          callback(transaction)
+        })
     })
 
     return transaction