Add Unit testing

[Gregory Benner]

It's an embarrassment that in 2017 I don't have any unit tests on this package...

So this is where I'll self-shame myself into doing it, and track my progress.

• refactor plugin to be more "test friendly"
• install and setup tape and a code coverage library
• track coverage with a service like coveralls.io and add a badge in the Readme.md
• Cover most of the "helper" functions