SciPy.mat is obsolete

[StuartLittlefair]

Used in the line below, and perhaps others, scipy.mat is no longer present in SciPy v12.

https://github.com/kgullikson88/Telluric-Fitter/blob/7ae98db278525e157d2d0abaf4697e2fe778d6bc/src/TelluricFitter.py#L62

This function is just an alias for numpy.asmatrix so a drop-in replacement of from numpy import asmatrix as mat should be an easy fix