Add attribute encrypted_data_bag_secret_key_path to Suite
Fix Omnibus installation on nodes using plain sh (vs. bash).
Support single cookbook with no dependencies and no Berksfile.

Closes #92
Merge pull request #77 from action-io/encrypted-data-bag-secret

Add attribute encrypted_data_bag_secret_key_path to Kitchen::Suite
Expose provisioner in driver configuration.

Exposes a new config file option: provisioner.

Defaults to `chef`.

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

Includes updates to docs and tests.