Support of ON DUPLICATE KEY for 'bulkCreate' method (only supported by mysql & mariadb)
By default, all attributes except 'createdAt' can be updated
Revert "Workaround to deal with an issue in node-webkit where the validate function fails on object literals"
Merge pull request #2692 from jcombes/master

Support of ON DUPLICATE KEY for 'bulkCreate' method (only supported by mysql & mariadb)