`from_smiles` function stacks molecules on top of each other when using multi-molecule strings

[jandestrada]

from qcio.models.structure import Structure 

structures = Structure.from_smiles("COCO.CC", force_field="MMFF94")

with open("/home/jdep/debug.xyz",'w+') as f:
    f.write(structures.to_xyz())
f.close()

If you open the file created you get something like this:

This might be an underlying issue in rdkit and probably not a qcio thing, but it would be detrimental to functionality here (since good luck getting that geometry to converge to something!)

pybel and openbabel for generating structures from smiles works well in this context, but switching dependencies could be annoying.

logging this here to bring attention to the problem

[coltonbh]

Solved with #50 .

Need to add charge information when generating smiles from structure.