title: pandoc: Unknown reader: gfm
body: <p>I'm trying to use <code>pandoc</code> (version 1.19.2.4) on Ubuntu 18.04 to render github flavoured markdown with:</p>
  
  <p><code>pandoc --from gfm --to html README.md</code></p>
  
  <p>This gives the error <code>pandoc: Unknown reader: gfm</code>.</p>
  
  <p>I guess I need to verify/install <code>gfm</code>, but its not clear how to do this.</p>
  
  <p>How do I fix this error? How do I use pandoc to generate github flavoured markdown?</p>