Add a brakeman/bundle-audit security check, fix a potential
vulnerability.
Update ChangeLog. [ci:skip]
Fix the serializer DoS bugfix from a prior commit.
Fix the progress-function call in the NERAnalyzer.
Dramatically refactor the word frequency analyzer.

We now have a separate "dataset segmentation" step, which comes in
to cut the dataset into configurable segments prior to the
collection of the word frequency analysis data. This should make
this code much easier to maintain and refactor.