Line fitting module

[lemmatum]

It would be handy to have a module for fitting spectroscopic line profiles (e.g. Gaussian, Lorentzian, Voigt). Looks like lmfit has a number of these built in already. So we probably just need to wrap it in some sensible defaults.

There may also be some automated fitters out there (in the wild) based on genetic algorithms or nonlinear least squares (like in the fityk program for x-ray scattering), which could be used to automatically identify the most prominent peaks in a spectrum featuring many lines.