made loading .mat files compatible to mac os

Made a switch for switching to Mac OS. The only difference is the
format of the directory for .may files.
Added new switch OVERLAP

change OVERLAP to True will fit the data to one gaussian but assume
that they are two gaussians of equal height and width overlapping. The
output will have two extra lists ‘h_from_sample’ (height of atoms from
sample) and ‘d_peaks’ (inferred distance between two gaussians that are
overlapping).
Merge branch 'mac_testing' into testing