Accept custom element classes via options.

[caike]

Accept custom classes for span elements (hours, minutes, seconds and clearDiv) and for timeout via a classNames option. Like this:

  $('#timer').startTimer({
    classNames: {
      hours: 'banana-hours',
      minutes: 'banana-minutes',
      seconds: 'banana-seconds',
      clearDiv: 'banana-clearDiv',
      timeout: 'banana-timeout'
    }
  });