Heroku Delux

For Heroku provider:

* make `git` strategy use https rather than ssh
* move ssh logic to `git-ssh` strategy
* make `api` default strategy
* have strategies inherit from one generic implementation rather than the git logic
Might want to make sure this doesn't get printed into the logs with the API key in plain text. Might be better to put in a `.netrc` to avoid it being in the URL.