moved transaction logic into transaction model

lib/sequelize.js

@@ -395,12 +395,7 @@ module.exports = (function() {
 
     Utils.tick(function() {
       transaction.prepareEnvironment(function() {
-        self
-          .getQueryInterface()
-          .startTransaction(transaction, {})
-          .success(function() {
-            callback(transaction)
-          })
+        callback(transaction)
       })
     })
 

lib/transaction.js

@@ -40,13 +40,21 @@ Transaction.prototype.prepareEnvironment = function(callback) {
   var self = this
 
   this.setIsolationLevel(function() {
-    console.log('aha!')
     self.setAutocommit(function() {
-      callback()
+      self.begin(callback)
     })
   })
 }
 
+Transaction.prototype.begin = function(callback) {
+  this
+    .sequelize
+    .getQueryInterface()
+    .startTransaction(this, {})
+    .success(callback)
+
+}
+
 Transaction.prototype.setAutocommit = function(callback) {
   this
     .sequelize