add name of cookbook to metadata.rb to stop Ridley complaining

Ran into the following when testing this cookbook locally with chef-zero:

Ridley::Errors::MissingNameAttribute: The metadata at 'chef/cookbooks/chef-whitelist' does not contain a 'name' attribute. While Chef does not strictly enforce this requirement, Ridley cannot continue without a valid metadata 'name' entry.

I have added the missing name attribute to the metadata.rb.