Reorganizes script into an executable class.
Shortens methods.
Adds simple command-line usage instructions.
Adds business objects, smaller methods.
Moves `uniq` from `csv_write` back to `csv_read`.

Makes more sense to remove dupes from the internal data structure
on reading the Lexington CSV rather than preserving them until
output.
Merge pull request #4 from openlexington/class_it_up

Refactor into a class for external usage