Write the QM thermo entry to libray only if QM calculation was successful.
Do not fail when QM attempt is unsuccessful in Gaussian.

Return None for thermo so that that it can fall back to group additivity, same
as for Mopac.
Fixed bug for QM when no thermo found for radical.
Allow selecting Hindered rotor fit in cantherm

Some time the best fit gives a negative energy barrier.
Therefore I added the ability to change the fit type to cosine
or fourier.

Also added an exception and error message for when this happens

Finally added more messages to the verbose log of cantherm to
help debug which rotor this occurs on.
Merge branch 'master' of github.com:GreenGroup/RMG-Py
Fix stray commas creating tuples accidentally.
Correction to commit bd8da7b