How might we handle cases where the ner_model.dat cannot be found?

[stevepolitodesign]

This relates to #60.

If it's challenging to configure the ner_model.dat in production-like environments, the Gem won't work, since it currently requires this file to exist.

[stevepolitodesign]

One solution could be to disable it?

TopSecret.configure do |config|
  config.model_path = nil
end

[stevepolitodesign]

This was addressed in #65