hubble-fit: diagrams, fit (broken)
hubble-fit: diagrams, fit (broken)

Copy of the Python code for everything but the covariance matrix (and
associated calculations). Hubble diagram's fit gives an incorrect omgM.
Left to do : fix fit, cosmetics on the diagrams, cov matrix.

lsst-lpc/hubble-fit,lsst-lpc/hubble-fit,lsst-lpc/hubble-fit