task/ta-npi-016-17 -- factor out RESTful SMS API

nparcel/conf/nparceld.conf
* placeholder for the new "rest" section

nparcel/config.py
* new attribute, rest
* updated parse_args() method to read the "rest" section

nparcel/loader.py
* __init__ now support API initialisation via the new "api" argument

nparcel/smser.py
* new attribute, api
* __init__ now support API initialisation via the new "api" argument
* send method now checks for a defined api before attempting the SMS
  send