title: Missing Dependency: rdiscount
body: <p>I am trying to build a site using jekyll, I have install <code>jekyll</code> and as the next requirement I have also done <code>sudo gem install rdiscount</code></p>
  
  <pre><code>Successfully installed rdiscount-2.1.7
  Parsing documentation for rdiscount-2.1.7
  Done installing documentation for rdiscount after 0 seconds
  1 gem installed
  </code></pre>
  
  <p>but when I try to start the jekyll server I get the following error:</p>
  
  <pre><code> $ [sudo] gem install rdiscount
    Conversion error: There was an error converting '_posts/1970-01-01-placeholder-post.md/#excerpt'.
  
               ERROR: YOUR SITE COULD NOT BE BUILT:
                      ------------------------------------
                      Missing dependency: rdiscount
  </code></pre>
  
  <p>Looks like it doesn't recognize the rdiscount,  I am on a mac and use homebrew to do package management. I am not familiar with the ruby or rubygem language (Come from python background). What might be the issue here?</p>