Persistence:

    p = persistence(f)
    dgms = init_diagrams(p,f)   # should use simplex data

    p = fast_persistence(f)
    p = cohomology_persistence(f)

    - Standard reduction
    - Row reduction

    - CohomologyPersistence
    - ReducedMatrix:
        - OrdinaryPersistence
        - OrdinaryPersistenceNoNegative


 - Vietoris-Rips should accept a NumPy array.

 - Alpha-shapes
