Allows to disable deobfuscation in find.

This PR allows to set an option to find to disable the deobfuscation of the id.

I needed that feature, because carrierwave is using find with self.id during an update and I didn't want to crypt the id again. Probably this is a better approach for reloading the model, too.

Here is how the fix for carrierwave with obfuscate_id and updating model looks like:
```ruby
mount_uploader :file, PictureUploader
def find_previous_model_for_file
  self.class.find(to_key.first, no_obfuscated_id: true)
end
```