Added rmg.unirxn.mastereqn module.
Added rmg.unirxn.mastereqn module.

This module, another written in Fortran, provides efficient functions related
to working with the full master equation matrix. This includes the calculation
of the collisional matrix blocks.

pierrelb/RMG-Py,enochd/RMG-Py,nickvandewiele/RMG-Py,comocheng/RMG-Py,nyee/RMG-Py,nyee/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,faribas/RMG-Py,pierrelb/RMG-Py,chatelak/RMG-Py,KEHANG/RMG-Py,enochd/RMG-Py,comocheng/RMG-Py,KEHANG/RMG-Py,faribas/RMG-Py