If config.json is present and user.privatekey has an ssh-rsa private key defined as well as a user.name, the SSH server will staticlly authenticate to whatever host is specified on the URL with those credentials.
The ssh-rsa private key must have is line returns replaced with the litaral \n
Example: "-----BEGIN RSA PRIVATE KEY-----\nblahblahblah\n"
* Accept default username/password overrides from config. Clarified supplying custom config. (#146)
* feat(auth): username and password may now be sourced from config.json fixes#104
