Modified getMcGowanVolume method to include sulfur.

This method is used when calculating diffusivities in liquid phase. I
removed all the other unused elements, too.
Conflicts:
	rmgpy/data/solvation.py
Adds saveEntry() method for solvation database.

Writes string representation of solute or solvent information.
Fixes some old ambiguities in the solvation database.

The solvation database encompasses both solute and solvent
data. Also, we have a solute library that is now used.
Use the default families for liquid-phase example.

I don't know if this is correct or not, but it doesn't work with all the families.
Merge pull request https://github.com/GreenGroup/RMG-Py/pull/236 'bslakman-solvation-fixes'
Clean up print statements when loading kinetic depositories.