added an unit test of ring corrections for two-ring molecule
added an unit test of ring corrections for two-ring molecule

chatelak/RMG-Py,pierrelb/RMG-Py,nickvandewiele/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,nyee/RMG-Py,pierrelb/RMG-Py,nyee/RMG-Py