Utility for handling number-sequences of all shapes and sizes.
TODO: new usage
To do:
- Word "AND" behavior.
- Selective convertion from one form to another.
- Refactor {nth.nthalize.iter_number_spans} to be able to split spans if a number is less than one that precedes it, or if a later period is less than a prior period. Probably need to break things out into several helper functions.
Goal concerns:
- Allow underscores in decimal sequences? e.g. "123_467_890"