title: Multiple Axis with Plots.jl
body: <p>Is there a way to have the second dataset plot on a separate axis, overlaid on the first plot? </p>
  
  <pre><code>using Plots; gadfly(size=(800,400))
  
  plot(Vector[randn(100)], line = ([:green], :step))
  
  plot!(Vector[randn(100)], line = ([:red], :step))
  </code></pre>