It turns out that `GridSearchCV` was being used instead of `Baart` every
time, which is why I thought `Baart` was working. That bug has been
fixed, but `Baart` might still not be working properly. It needs to be
tested on a large sample of stars to see if it does or not.

On a separate note, I have reorganized the command line arguments, so
that they are categorized in groups. I have also explicitly stated what
the default value of each option is in the help string.

The default value of `--min-phase-coverage` has been changed from `1/2`
to `0`.