'validate' hooks aren't called when updating a model

[miguelcoba]

The 'validate' hooks are not being executed when updating a model.
If some bussiness rule is enforced on creation of a new model, almost surely they will need to be enforced on updating the model.
For example, for a User model, the salt and hash are generated from the password attribute. When updating a User, if the password is changed a new salt and hash should be generated. Also, if the password isn't present when updating, the validate hook could detect it.

Way to fix it:
Apply validate hooks on update.

[christiansmith]

Done.