code: function permissions (user, modelName, callback) {
      return get(modelName, true).getPermissions(user, callback);
  }
docs: Retrieve the permissions DSL for a model
  @param  {Object}   user      The user to which the permissions should be customised
  @param  {String}   modelName The name of the model
  @param  {Function} callback  A callback to return the permissions DSL to
  @return {Void}