Fixed transcription error for sulfur experimental Hf

Enthalpy of formation should be 65.66 kcal/mol, as in Gaussian
whitepaper.  Also added bond additivity correction for S-H
(even though it's 0).
Adding sulfur atom energies for CCSD(T)-F12.

Adding sulfur atom energies for CCSD(T)-F12a and F12b, with the
basis sets cc-pVDZ-F12, cc-pVTZ-F12 and cc-pVQZ-F12
Changing incorrect comma to colon.
Merge pull request #269 from cclass86/sulfur

Updates to sulfur thermo in statmech.py