How can one test slush generators? 

Ref: http://stackoverflow.com/questions/37812706/how-can-one-automate-tests-of-slush-generators

I envision doing something like this:

package.json:

```
....
  "scripts": {
    "test": "slush . test-placeholders.json && cd output && npm test"
  },
....
```

to run the tests of the scaffolded project, if that makes sense
