Fixes testing generator errors

* Adds `debug` flag to generator tests
* Essentially, Thor's default behavior is to print the error message
  instead of raising an exception. Adding the `debug` flag allows us
  to raise the exception explicitly.
  * See: https://github.com/rails/rails/issues/14416
* Cleans up empty lines
* Adds `minitest/pride`
Merge pull request #222 from dockyard/thor-errors

Fixes testing generator errors