title: Integrate opalrb with sprockets on sinatra
body: <p>I'm wanting to integrate Opal into my next project and decided to just move onto sprockets from sinatra-asset-pack, however I can't find anything on how to integrate opal into sprockets rather than just setting up sprockets and opal separately.</p>
  
  <p>How do I set up sprockets and integrate Opal.rb with it?</p>
  
  <p>Bearing in mind I don't run it as a rackup file, this is due to our environment so it's just not viable, instead I bundle my app as a gem and run it via executable.</p>
  
  <p>Or perhaps just point me in the right-direction to do this if some resource on this already exists and I just wasn't able to find it, that would be fab as well.</p>