Add Chlorine to list of atoms in Cantherm statmech module.
Add Chlorine to list of atoms in Cantherm statmech module.

nickvandewiele/RMG-Py,comocheng/RMG-Py,enochd/RMG-Py,pierrelb/RMG-Py,chatelak/RMG-Py,pierrelb/RMG-Py,nyee/RMG-Py,nyee/RMG-Py,comocheng/RMG-Py,nickvandewiele/RMG-Py,enochd/RMG-Py,chatelak/RMG-Py