添加Poormanscron模块，这个模块能够不依赖系统来完成drupal的任务。

drupal需要定期执行一些任务，否则搜索等功能无法完成！

  1. A module which runs the Drupal cron operations without needing the cron application.
  2.  
  3. For every page view, this module checks to see if the last cron run was more than 1
  4. hour ago (this period is configurable). If so, the cron hooks are executed,
  5. and Drupal is happy. These cron hooks fire after all HTML is returned to the browser,
  6. so the user who kicks off the cron jobs should not notice any delay.