title: Markdown doesn't work in attachments
body: <p>I'm creating a Slack integration with the Slack API. I followed <a href="https://api.slack.com/docs/formatting">the documentation</a> but the markdown formatting doesn't work on my attachments...</p>
  
  <p>Here is my response object:</p>
  
  <pre><code>{
    response_type: "in_channel",
    text: "List:",
    attachments: [
      { 
        text: "*pseudo*:\nbla bla bla",
        mrkdwn: true
      }
    ]
  }
  </code></pre>
  
  <p>The "*" are displayed and not evaluated. Did I make a mistake? </p>