Investigate delete on cascade when defining associations

[russnicoletti]

While working on #228, it was discovered the delete hooks (beforeDelete, afterDelete) are not run during /DELETE requests. From the Sequelize documentation: "The only way to call beforeDestroy/afterDestroy hooks are on associations with onDelete: 'cascade' and the option hooks: true"

We should investigate whether using 'delete on cascade' when defining associations results in delete hooks being run during /DELETE requests.