defect/de-07 -- Alerting Error Notifications to be Environment
Specific

nparcel/restemailer.py
nparcel/smsemailer.py
nparcel/utils/files.py
* factor out the templated-based message construction into a separate
  function, templater()
* update the create_comms() method to use the
  nparcel.utils.files.templater() function

nparcel/restemailer.py
* refactor the get_subject_line() method to use the
  nparcel.utils.files.templater() function

nparcel/comms.py
nparcel/restemailer.py
* refactor the send_email() method to support the refactored
  nparcel.restemailer.get_subject_line() method
* move the subject generation logic from the process method into the
  nparcel.restemailer.create_comms() method