title: What is the best way to check if an addon is a new install or has an update when using the Firefox addon SDK?
body: <p>I'm developing an addon with the addon SDK (no restart).</p>
  
  <p>What would be the best way to check if an addon has just been updated or installed for the first time?</p>
  
  <p>I would like to open a new tab with a changelog or recent changes upon install or update (no restart).</p>