can't crawl crawl hidden form content not shown in the page source

I have to crawl the comments in this web page http://ift.tt/1KQISS8

  <section class="comments-container">
  <div class="meta-information">
  <a data-disable-with="Loading…" data-decremented-comments-count="7 Comments" class="comments-count" data-remote="true" href="/statuses/6587/comments">8 Comments</a>
    <span class="last">
    <span class="last-commenter">last comment by</span>
      <a class="user secondary-highlight-hover" href="/users/cathyl">
    <img class="avatar" src="/images/user.png" alt="User" />
      <h2>CathyL</h2>
</a>
    <span class="last-comment-time"><time datetime="2015-06-19T10:43:10-04:00" class="relative" title="Fri, Jun 19, 2015 at 10:43:10 AM" data-time-ago="2015-06-19T10:43:10-04:00">06/19/20115</time></span>
  </span>
</div>

from the page source it's form but the source doesn't show the any comments contents

when I open the website: http://ift.tt/1KQISS8, I can see the comments.

How do I crawl them when the source code doesn't show the form content? any suggestion or examples？ Thanks very much!