title: inline images with ruby mail gem
body: <p>Sorry if I'm missing a good article, but I can't find a good example on how to use inline images using ruby with the mail gem (I'm not using RoR)
  The best example I could find is <a href="https://stackoverflow.com/questions/16736878/html-email-with-inline-images-not-rendered-properly-in-iphone">here</a>, but I don't understand where the <code>.cid</code> method comes from.</p>
  
  <p>here's an excerpt from the above mentioned post where the <code>.cid</code> method is used.</p>
  
  <pre><code>html_part do
      content_type 'text/html; charset=UTF-8'
      body "&lt;img width=597 height=162 id='Banner0' src='cid:#{pic.cid}'&gt;"
  end
  </code></pre>
  
  <p>I have the mail gem working and it can send images as attachments but I need them to be displayed inside the email, without having the need to open attachments.</p>