Fix for molecules with more than one aromatic rings
Fix for molecules with more than one aromatic rings

if the molecule has more than one aromatic rings and only
some of them are kekulized, the checkForExistingSpecies will fail.
By running generateResonanceIsomers, it will create isomers with fully
kekulized version, which makes checkForExistingSpecies work again

nickvandewiele/RMG-Py,nyee/RMG-Py,pierrelb/RMG-Py,pierrelb/RMG-Py,nyee/RMG-Py,nickvandewiele/RMG-Py