Use H298 and S298 directly from ThermoData when fitting Wilhoit in RM…

…G jobs.

This way we don't have to worry about bugs in the getEnthalpy() or
getEntropy() methods, such as the one most recently fixed.

rmgpy/rmg/model.py

@@ -84,8 +84,8 @@ def generateThermoData(self, database, thermoClass=NASA):
         elif isinstance(thermo0, ThermoData):
             Tdata = thermo0._Tdata.value_si
             Cpdata = thermo0._Cpdata.value_si
-            H298 = thermo0.getEnthalpy(298)
-            S298 = thermo0.getEntropy(298)
+            H298 = thermo0._H298.value_si
+            S298 = thermo0._S298.value_si
             Cp0 = thermo0._Cp0.value_si
             CpInf = thermo0._CpInf.value_si
             wilhoit = Wilhoit().fitToDataForConstantB(Tdata, Cpdata, Cp0, CpInf, H298, S298, B=1000.0)