In any event, the tutorial is great and I was breezing through it until I got to the step where I needed to push to Heroku. I kept running into the error:
I spun my wheels for a bit following the instructions nitrous.io instructions on how to connect nitrous with github. But didn't find the answer until I paid better attention to the Heroku help page. Obviously (in hindsight), if I get a publickey issue when pushing to Heroku, I should look at that help page instead of connecting to github.
Permission denied (publickey).
In any event, if you get a publickey error pushing to Heroku from nitrous.io, I got it to work by running the following command in the terminal:
$ heroku keys:add