bugs in absorption_spectrum_fit

[w-ux]

Hi,

I've found some bugs while fitting absorption spectrums using trident, in trident/absorption_spectrum/absorption_spectrum_fit.py, line 827:

q=(b[2]-b[1])/4

Which will lead to a TypeError sometimes in line 828:

cut = yDat[b[1]+q:b[2]-q].argmax()+b[1]+q

I changed line 827 to:

q=(b[2]-b[1])//4

But not sure if it works properly.