added reverse coefficent test for ThirdBody format
added reverse coefficent test for ThirdBody format

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