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?
Ok, so Imho, the code could be improved to show the intended scenario. I know that have the rescue block, but when you read the code becomes more clearly all the scenarios.

```ruby
   begin
      original_value = record.attributes_before_type_cast[attribute.to_s]
      Date.parse(original_value)
   rescue ArgumentError => exception
      record.errors.add(attribute, 'invalid date')
   end

   record.errors.add(attribute, 'must be in the past') if value && (value.today? || value.future?)
```

Wdyt?