Should NER filters be disabled by default?

[stevepolitodesign]

As mentioned in #60, the ner_model.dat file is large, and it's not advisable to store it in version control. This isn't a problem for local development, but is a problem for production environments that are built from source.

Because of this, it may not be possible to easily use the gem in a deployed environment. In #65, we allow the gem to be configured such that we can disable NER filters. But, should that be the default?