Add Code Coverage

A new devDependency is required ot carry out code coverage. It has
been added to "package.json". ".travis.yml" has been changed to have
an `after-script` run which processes the coverage reports
Add Coverage Badge

A svg badge has been added to README.md for display to the developers
Merge branch 'coverage' into develop

New Development Feature: Code Coverage

The code will be covered and its reports processed using instabul
and reports put up on
https://coveralls.io/r/forfuture-dev/node-simple-argparse