Consider ditching SpecFlow and using regular nunit style tests

[nbarnwell]

I'm just working on adding support for a command to set the default path for ADR files, and most of my time has been spent wrangling SpecFlow. I could have written a single nunit test and just got on with things, but TDD is a real pain with so much boilerplate.

It's your game, so it's your rules, but I gotta tell ya, I wouldn't be upset if I could submit a PR to simplify it by removing SpecFlow entirely from the solution... :)