Provide verbose debug output

[colincasey]

The information provided by the deployer is useful when everything works as expected. But when the deployer is failing, it's unclear what is happening internally. It would be helpful for troubleshooting purposes to see information such as:

• HTTP request/response information
• Config values used and where they are sourced from
• And any other useful actions being taken

Preferably this would also be triggered by the inclusion of the DEBUG=* environment variable that is frequently used for diagnostic purposes in the Heroku CLI (or the Java plugin for the CLI configures some verbose flag based on DEBUG).