code: function deleteGroup(connections, options, groupParams, cb) {
    var validate = validation(groupParams);
    function validateParams(cb) {
      validate.has("_id", cb);
    }
    validateParams(function(err) {
      if (err) {
        return cb(err);
      }
      var conn = connections.mongooseConnection;
      var groupsModel = models.get(conn, models.MODELNAMES.GROUPS);
      groupsModel.findById(groupParams._id).remove(cb);
    });
  }
docs: /*
  deleteGroup(connections, options, group, cb)
  
  connections: {
  mongooseConnection: ...
  }
  
  options: {
  uri:       db connection string,
  userEmail: user email address string
  }
  
  group: {
  _id: id of the group
  }
  
  cb  - callback function (err)