def notification(notifier, opts = {})
      Guard.state.session.guardfile_notification = { notifier.to_sym => opts }
    end
def notification(notifier, opts = {})
      Guard.state.session.guardfile_notification = { notifier.to_sym => opts }
    end
Set notification options for the system notifications.
 You can set multiple notifications, which allows you to show local
 system notifications and remote notifications with separate libraries.
 You can also pass `:off` as library to turn off notifications.

 @example Define multiple notifications
   notification :ruby_gntp
   notification :ruby_gntp, host: '192.168.1.5'

 @param [Symbol, String] notifier the name of the notifier to use
 @param [Hash] opts the notification library options

 @see Guard::Notifier for available notifier and its options.