Restored source/rmg/ctml_writer.py.
Restored source/rmg/ctml_writer.py.

Has been inadvertently deleted last month.

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