Dependencies: Remove Pymatgen #5
Description
Currently, Pymatgen is a dependency only for loading in the Mendeleev numbers in order to sort the correlation plots.
The entire Pymatgen package is not necessary for this, so a future update should aim to remove Pymatgen as a dependency and instead include a dictionary of {element:mendeleev_number} key:value pairs within the data directory of this repository which can be used to obtain the Mendeleev numbers