Fix  #363, run endSubmit even if no after hooks are defined

Why:
- if I submit, but fail validation the button can stay permanently disabled
 - `beginSubmit` runs and change button to `disabled`, but `endSubmit` is sometimes missing
 - only present if `afterHooks` are missing

Workaround for ppl using older version, add empty `after` hook, e.g.:
```
AutoForm.hooks({
  updateItem: {
    after: {
      update: function () {} // No-op to avoid auto-form bug
    }
  }
})
```

However, ideally we shouldn't need that workaround.