Remove validates_timeliness

This library has been abandoned, has been producing deprecation warnings and is only used to validate a single field so remove it and perform the validation ourselves.

This is of arguable value but the deprecation warnings were annoying me. Also, the validator is only tested by the model specs.

Any opinions?
Yeah. But you can extract to a method if you like:

```ruby

  check_invalid_date(record, attribute, original_value) if value.blank?
  record.errors.add(attribute, 'must be in the past') unless value.blank? or value.past?
  
  def check_invalid_date(record, attribute, original_value)
    Date.parse(original_value) if original_value.present?
  rescue ArgumentError
    record.errors.add(attribute, 'invalid date')
  end
```

check_invalid_date is not the best name but you can rename to something  better, =).