Added a couple of tests to exercise rwmol to mol
Added a couple of tests to exercise rwmol to mol

These tests validate RWMolecule to Molecule, and back again. They
hopefully also serve as a simple example of using the link both
ways.

OpenChemistry/avogadrolibs,ghutchis/avogadrolibs,ghutchis/avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,OpenChemistry/avogadrolibs,OpenChemistry/avogadrolibs,ghutchis/avogadrolibs,OpenChemistry/avogadrolibs,ghutchis/avogadrolibs