Fixing query generation error when calling save() on an Instance

When the raw value of ```id``` is stored as ```identifier``` in ```save()``` an invalid query is returned from the ```QueryGenerator```.

i.e. - Without the fix, an UPDATE query looks like this:  
```UPDATE `Users` SET `gender`='male',`email`='updated@bar.com',`updatedAt`='2013-05-29 23:33:36',`createdAt`='2013-05-29 23:33:36' WHERE 2```  

The ```WHERE 2``` is not the desired behavior. If ```id``` is wrapped in an object then the correct query is generated:  
```UPDATE `Users` SET `gender`='male',`email`='updated@bar.com',`updatedAt`='2013-05-29 23:33:36',`createdAt`='2013-05-29 23:33:36' WHERE `id`=2```

lib/dao.js

@@ -158,7 +158,7 @@ module.exports = (function() {
     else if (this.isNewRecord) {
       return this.QueryInterface.insert(this, this.QueryInterface.QueryGenerator.addSchema(this.__factory), values)
     } else {
-      var identifier = this.__options.hasPrimaryKeys ? this.primaryKeyValues : this.id;
+      var identifier = this.__options.hasPrimaryKeys ? this.primaryKeyValues : { id: this.id };
 
       if (identifier === null && this.__options.whereCollection !== null) {
         identifier = this.__options.whereCollection;