task/ta-npi-022-04 -- HTML email structure

nparcel/images/
nparcel/templates/
* new templates and images to support HTML email structure
task/ta-npi-022-05 -- REST emailer send

nparcel/restemailer.py
* introduced structure similar to the email send so that we can
  prepare the message with MIME multi-parts
* added the sender attribute the __init__() method
* new method xxx() as a placeholder to replace the existing send()
  method
* new method validate() to run a basic check over the email address