Ensure that destroy option is respected when --parallel is used.
Merge pull request #99 from opscode/ssd/fix-parallel-destroy

Ensure that destroy option is respected when --parallel is used.
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.