title: Play a graph line about the time in javascript
body: <p>I am discovering the amazing Rickshaw library !</p>
  
  <p>There is one thing i am not sure i can do, i would like to "play" my graph line.</p>
  
  <p>I mean, when i click a button, i would like to have like a vertical line (representing the current time), which go strait, the left part of the line would be a different color (representing the past) than the right part (representing the futur).</p>
  
  <p>Is it possible to build this kind of thing (a graph that we can "play" about the time) wich Rickshaw?</p>
  
  <p>If not, do you know a javascript library which enables that?</p>