Adds some unit tests for the solvation module.

This includes tests for: setUp, obtaining solute parameters from a library,
calculating and setting the McGowan volume for a solute, calculating solute
diffusivity, and calculating solvent viscosity.

The main method was also edited so that the unittest can be run on its own.

Along the way fixed a floating point error in calculating diffusivity.
Solvation module raises a DatabaseError when solvent is
not found in library. Unittests updated with a solvent library
test.

Conflicts:
	rmgpy/data/solvation.py
Cleaned up tests for Abraham parameter estimation and solvation
correction calculation.

Nitrogen and sulfur cases commented out for now, fixing is work in progress. Removed many test cases, so only have a few for each test.
More consistent naming of libraries in solvation module.

Used SolvationDatabase.libraries to store the solute and
solvent libraries rather than giving them their own variables,
to maintain consistency with the other types of databases. Changed
unit test to reflect the change.
Merge pull request #243 from bslakman/master

Solvation unit tests looks good to me. Tests all seem to pass.
Notice that:
    SolvationDatabase.solventLibrary
    SolvationDatabase.soluteLibrary
have been replaced with:
    SolvationDatabase.libraries['solvent']
    SolvationDatabase.libraries['solute']
which makes things more consistent with other types of database.
add missing method argument in thermoEstimator example input file

This crashed the thermoEstimator.
Make statmech depositories a dictionary.

Now it is consistent with thermo depositories.  Otherwise
it does not make sense to store a default dictionary but then
replace with the StatmechDepository object.  Also this allows us
to add more depositories in the future as necessary.
Fix statmech groups saving error.

Groups cannot be saved directly. self.groups is a dictionary.
Implement getAllSoluteData method in solvation.

This returns all the possible solute descriptors for a species, which if in the library, includes the library set, and always includes the group additivity estimate.
Better documentation for some solvation methods.

Added information about units for the solvation correction to thermo.
Merge pull request #249 from bslakman/master

Solvation updates
QM fix: Only use one rotational constant for linear molecules.

The rmgpy.statmech.rotation.LinearRotor.rotationalConstant expects only a single value.
But MOPAC or similar (via cclib) returns a moments of inertial result in an array, like
   B = ([0, 68.4, 68.4], "cm-1").

I assume (as had @keceli in his version of this fix 210ea35697c725594e96a9c56e019aa61a8256b8)
that we want to use the highest of the frequencies (as opposed to the sum or anything fancy?)

If this is right, it closes #250
Update RMG example 1,3-hexadiene with multiplicity label
Update RMG example c3h4 with multiplicity label
Update RMG example ch3no2 with multiplicity label
Update RMG example diesel with multiplicity label
Update RMG example e85 with multiplicity label
Update RMG example liquid_phase with multiplicity label
Update RMG example methylformate with multiplicity label
Update RMG example minimal with multiplicity label