cut high-gravity (logg>5.5) part of grid

effected as part of the script, not actually a new limit in the fit
I should probably eventually write an option into make_model
fixed syntax for deleting model parameters
moved check on model limits to __call__ from interp_models
added lots of logging statements, why is it not interpolating?

Interpolation isn't always happening properly - sometimes the output
flux is just the nearest grid point
fixed interpolation problem - with 2 spectra left, bug ensued

When there were only two spectra to be interpolated, the code had
a bug that meant it wasn't actually interpolating, just grabbing the spectra
for that grid point.

Also I had mixed up selecting the upper and lower values for interpolation
that's been changed
script to check that the grid is actually being interpolated
expanded initialization range; stopped cropping burn-in for now

stopped cropping burn-in until I determine why the fit narrows
so fast
changed logging level
Merge branch 'master' into mask