title: Whitespaces from my keyboard not interpreted in markdown titles
body: <p>The spaces I type with my keyboard are not recognized in my markdown titles in (at least) atom syntax highlighting and some online markdown editors such as commonmark (<a href="http://spec.commonmark.org/dingus/?text=%23%20Try%20CommonMark%0A%0A%0A%23%23%20Title%20with%20space%20c%2Fc%20from%20above%0A%0A%23%23%C2%A0Title%20with%20from%20keyboard%0A" rel="nofollow noreferrer">see example</a>): </p>
  
  <p>I run on ubuntu 16.04 LTS.</p>
  
  <p>Any idea why this is happening ?</p>