title: mocha doesn't clean the environment between re-runs when watching
body: <p>So I have noticed in the past that if I change some code inside callbacks when running <code>mocha --watch</code> the changes aren't picked up. I need to kill it and restart it.</p>
  
  <p>This usually isn't a big problem.</p>
  
  <p>However, I'm now managing some states in some callbacks (<code>sequelize hooks</code>) and my tests will always fail when running more than once. I keep <code>mocha --watching</code> my code as I write it, and it gets really annoying to restart it every time. Basically I can't use the <code>--watch</code> feature anymore because the old callbacks are running with stale state.</p>
  
  <p>Is there a way to have it reload everything as new?</p>