Clean up, simplify, add more style & integration tests

Biggest functionality changes are in c82652b, which we've been using in production since late November. The bump to 1.0.0 reflects that fact.

Additional, more recent changes clean up a lot of code style issues (thanks Rubocop!)

Rakefile has been tweaked, adding more testing:

* Rubocop
* Test Kitchen (no actual integration tests yet)
* Chefspec (no actual unit tests yet, just a stub)

Travis will only run the style & unit(less) tests, as the integration tests (such as the might be) require resources likely beyond Travis (VMs & the like).

A number of these changes are opinionated, so I welcome discussion.