Allow to override sudo.
Merge pull request #102 from calavera/optional_sudo

Allow to override sudo.
Expose provisioner in driver configuration.

Exposes a new config file option: provisioner.

Detects if it is being init'ed in a Module or a Cookbook and defaults to
the right provisioner.

Passed to the driver as the `provisioner` configuration
item.

Includes updates to docs and tests.