Wrote a calculator of the Cramer-Rao lower bound for the variance of the MLE.
The DTI model now starts with the gaussian linear model fit for DTI.
I changed the loglikelihood function (for gaussians) to now use a scaled version of the bessel functions (gsl_sf_bessel_I0_scaled).  This made some terms that I think were previously being ditched or lost somehow work, and let me include a term (x - nu)^2, which feels good.  Loglikelihoods now correspond to what I think they should, and I'm no longer getting values that make it look like a succesful MLE is worse than the starting point.
Merge pull request #6 from patrickeganfoley/justXForDTI

Just x for dti