Catch novel non-convergence error. Not catching these had made it so that model fitting would just quit because the program thought it was a different kind of error the user had to figure out (e.g., syntax).
Removed errant time_scheduled_continuous argument in ncs_mmrm_fit().
Improved pkgdown site, categorizing functions in the function reference.
Improved README, basing it on survival::pbcseq instead of randomly generated data.