code: def update(new_email_address, name, custom_fields, resubscribe, 
        consent_to_track, restart_subscription_based_autoresponders=false)
        options = {
          :query => { :email => @email_address },
          :body => {
            :EmailAddress => new_email_address,
            :Name => name,
            :CustomFields => custom_fields,
            :Resubscribe => resubscribe,
            :RestartSubscriptionBasedAutoresponders => 
              restart_subscription_based_autoresponders,
            :ConsentToTrack => consent_to_track }.to_json }
        put "/subscribers/#{@list_id}.json", options
        # Update @email_address, so this object can continue to be used reliably
        @email_address = new_email_address
      end
docs: Updates any aspect of a subscriber, including email address, name, and
   custom field data if supplied.