def config_value_for(key, default = nil, check_live = true)
      key = key.to_s
      value = check_live ? self[key.to_s] : nil
      value || config[key] || self.class.config_value_for(key) || default
    end
def config_value_for(key, default = nil, check_live = true)
      key = key.to_s
      value = check_live ? self[key.to_s] : nil
      value || config[key] || self.class.config_value_for(key) || default
    end
Returns the value for a configuration option (mapping to an
 environment variable). If check_live is true (which it is
 by default), it will also check the environment for a value.