Qchem Module for Cantherm

Added a module for cantherm that allows users to perform rate theory calculations with Qchem output files. Similar to the Gaussian module. Added a couple simple examples as well.

Reformulating pull request https://github.com/GreenGroup/RMG-Py/pull/255 so that isopentoxy example creation and deletion are omitted (they cause git to slow down quite a bit.)