Added units to wilhoit parameters for monatomic spc

Cantherm was throwing an invalid quantity error for
species like H as the units were not explicitly
mentioned for wilhoit parameters. The units added are
Cp, Cp0 and CpInf (J/(mol*K))
H (J/mol)
S (J/(mol*K))

The output was checked for H atom with primary thermo
library and looks okay.
Merge branch 'master' of github.com:GreenGroup/RMG-Py