'heroku-run' should accept callbacks for its API queries instead of accepting a client object

[vedantgoyal]

Do you want to request a feature or report a bug?

enahncement

What is the current behavior?

'heroku-run' exports a Dyno class to create new dynos or run commands inside existing dynos. It takes a parameter called 'heroku' which is the api client used by the Dyno class to create or find a dyno.

What is the expected behavior?

It would be preferable for the Dyno class to take api callbacks as a parameter instead. This will make reusing this module much simpler. Currently a heroku client has to be emulated and passed as a parameter to make different api calls.