title: Good RoR Gravatar gem/plugin and detect if the gravatar account exists or not
body: <p>I'm currently using mdeering's gravatar_image_tag plugin to get gravatar images for users but my dilemma is to try to detect in the code if the user has a gravatar:</p>
  
  <p>If he does then display the gravatar image.
  If not, then display a local default image file on my server.</p>
  
  <p>I'm open to using other plugins if they offer this functionality.</p>
  
  <p>Please provide code examples.  They help me learn the best.</p>
  
  <p>Thanks!</p>