Minor bug fixes, file cleanup

[nlk36701]

No description provided.

[sgoodlett]

There are a few things I think need changing/looking at.

• (molsym/molecule.py line 74) The constructor for molsym.Molecule from a Psi4 molecule requires that Psi4 be imported. Psi4 is not a MolSym dependency so there should be a check before execution for a Psi4 module. If there is none, we can just throw a helpful error message.
• (molsym/molecule.py line 78) Move comments to the start of the function for style consistency.
• (molsym/salcs/internal_coordinates.py line 1) Do we need to import copy if we are only using deepcopy?
• I'm suspicious of the internal_coordinates.py code and how it deals with what we call "phase". It seems like we calculate and apply a phase 3 separate times. Once in "ic_index", once in "operate_on_ic", and once in "get_fxn_map" (line 53).
• The new tests for Cartesian coordinate SALCs don't seem to test anything

[nlk36701]

I'm not sure where the tests for Cartesian coordinate salcs even came from haha. I'll remove that.
As for the IC coordinate phase stuff, it works perfectly with CMA for now but I'll take a look to see what can be cut out.